The build manual

• Photograph the certification jamb label and the yellow FMVSS reduced-capacity label; file them with the buyer's order. These two photos govern the whole build.
• Confirm commercial-vehicle insurance is active — it titles as a commercial step-van until Phase 13, and RV insurers will not touch it yet.
• Get written confirmation from a GM commercial dealer on parts, software support and open recalls for the VIN. Production ended 21 Oct 2025; get it in writing before money goes into the box.
• Line up covered workspace with 240 V power — bonding has temperature windows, and an EV without a plug is a daily logistics problem.
• Download the 25MY body builder manual no-drill zones and HV routing; print the underbody exclusion maps and the UI bulletin 191c airbag/no-drill diagrams. Every hole in Phases 4 and 8 gets checked against both.
• Submit a Math Data (CAD) request to GM Upfitter Integration for the 600's airbag zones, sensor/antenna locations and harness runs — bulletin 191c says its own diagrams are reference-only, and the request is free. Lead time unknown, so it goes in now, not at the design freeze.
• Photo-document the van's condition on arrival (bulletin 192c's delivery-inspection discipline) — every panel, the roof, the cargo box — before the first modification, while in-transit or dealer-prep damage is still claimable.

• ✅ CAT scale, as delivered — DONE 2026-09-07 (Fuel City Saginaw, CAT #2162, ticket 1216226250659): steer 4,640 / drive 4,660 / gross 9,300 lb with both occupants (330 lb) aboard → 8,970 lb van-only, Adrian Steel shelving still in. That's 450–1,150 lb over spec curb depending on trim — the strip-out delta (weigh gate 2) is now the number that matters. GVWR code confirmed C7E / 11,000 on the vehicle, so headroom at this weigh: 1,700 lb to GVWR, 651 lb front GAWR, 1,512 lb rear GAWR — the front axle caps anything mounted forward. Full analysis + ticket: research/weigh-ins.md in the repo. Weigh gate 1 closed.
• Strip the upfit — shelving, rails, partitions; patch and seal the abandoned holes.
• CAT scale, stripped — same scale (Fuel City Saginaw #2162, for comparability), same charge state. Weigh gate 2 — next up. Ticket 2 − 9,300 = what the strip actually returned; the 416 lb FMVSS deduction is assumed to come back, not known.
• Battery health check — charge to 100%, run a measured highway leg, log kWh dispensed vs indicated SoC. The charging plan assumes 173.3 kWh useful; verify it on this pack.
• One DCFC session at a working 150 kW+ station — confirm the 80–95 min 10→80% figure, and that fast charging works at all before you're 400 miles from home.
• Hose-test the bare van — even new vans leak, doubly true on a low-volume commercial body. Find water paths before insulation hides them.
• Inspect the roof at intended fan/solar locations; verify the M8 rain-gutter studs and solid (non-CC4) panel sections against this van, not the manual.

Run the SKU weight rebuild with the Phase 1 scale tickets as input. Then decide on paper and stop deciding: Plan C geometry with the bath bay held as storage · 16 gal fresh / ~22 gal grey · under-bench A/C (lock the unit here) · Espar S3 D2L · the §05 one-line diagram unchanged. Every cut in Phase 4 comes off this frozen drawing. A change after freeze costs a re-audit of the weight budget, by rule. Plan the whole interior at full scale — stopping at hand-drawn layouts was the self-declared most amateur mistake in the research corpus.

Degrease and scuff every bond area. Map every rib, no-drill zone and HV route from the printed maps onto the actual walls in tape. Dry-fit the floor deck, window sub-frames and fan garnish rings. Template every penetration in cardboard and tape it in place. Walk the layout at full scale — this is the cheapest day of the entire build to find a problem.

• Windows: bond aluminum sub-frames with 08115 (glass-bead bond line for thickness control), then set the windows into the frames. 4 hr clamped, 24 hr before glazing.
• 2 × MaxxFan: solid roof sections only, never CC4. Tape the area, cut to the cardboard template with a fine-tooth jigsaw blade, file the edge, frame the aperture, bond, seal — butyl under the flange, self-leveling lap sealant over every screw head. 24 hr before loading.
• Heater exhaust + combustion intake: thru-hull low on the body, clear of the underbody exclusion zones on the printed maps.
• A/C exhaust + condensate: the under-bench unit ducts condenser air out through the floor or a lower side panel — cut and seal that path now, plus the condensate drain.
• Shore inlet + glands: NEMA 14-50 inlet and every antenna/monitor gland, drilled and sealed now.
• Solar mounts: M8 rain-gutter studs only — zero new roof holes for the array.

To a genuine effective R-7 — over the ribs, not just between them. The ribs are thermal bridges; insulating only the bays leaves a radiator grid in the wall. Polyiso on the flats, Thinsulate SM600L on curves and rib returns, closed-cell foam strips over exposed ribs, nylon washers under bolts that would bridge. No vapor barrier, ever — condensation on cold metal can only be managed, not eliminated, so the assembly stays vapor-open where it needs to dry. Avoid fiberglass, denim, spray foam, and Reflectix-as-insulation. ~485 sq ft, ~63 lb in the audit.

Zero fasteners through the floor at any point — the Ultium pack owns the underfloor. The deck floats: wall framing traps it laterally, bonded aluminum cleats (08115) at the bulkhead and rear sill trap it fore-aft. Insulated floor is a non-negotiable. Cleat bonds get the full 24 hr cure before the deck is walked on.

• Every session touching the van's 12 V side starts with the bulletin 190b disconnect: ignition off, key out, meter the 12 V battery first — 13.5 V+ means Battery Maintenance Mode is live and the HV charger is energizing the cables; wait it out. Engage the HV service lockout and pin it. Disconnect the negative at the monitor-module stud only (unplugging the module = 4-hour relearn); re-torque grounds to 9 N·m.
• Van-side 12 V taps use the factory provisions only — the 188d battery/ignition circuit add or the 196b (9L7) blunt-cuts by the park brake (2 × 30 A relay-controlled + 10 A run-mode). DC-DC enable keyed to RUN, the water-heater/induction interlock signal, and any door-state trigger all ride these; nothing splices into an existing harness.
• Bench-commission the whole system before installing it: 2 × LiTime 24 V 230 Ah in parallel (equal-length paralleling cables) → 250 A Class T per battery → Lynx Distributor M10 → MultiPlus-II 24/3000 → single 120 V leg into a Blue Sea 8099, SmartShunt on the bank, Orion-Tr feeding the 12 V panel. Prove it works on a bench where mistakes are cheap.
• SmartSolar 250/60-Tr on the final roof array — panel count pending rooftop A/C layout; the 250 V input window is what makes cold-Voc safe if three panels remain viable.
• Set the MultiPlus AC input current limit to 8–16 A so the house is happy sharing one pedestal leg with the van's EVSE.
• Wire the A/C circuit to the max-mode draw, not a surge multiplier.
• Run everything possible on DC — fridge, fans, lights, pump, router. An idling inverter burns 10–30 W around the clock; that's real amp-hours overnight.
• Torque every lug, thread-locker on every bolt, label every wire, and tape the printed one-line diagram inside the electrical cabinet. You must know this system cold at 2 a.m. in Wyoming — that's why this row never gets outsourced.
• Then mount the panels, fly the array, and verify harvest on a real day.

Espar Airtronic S3 D2L, 2.2 kW: 5 gal aux diesel tank in the rear box (12 nights at 0.41 gal per 20 °F night), fuel line and dosing pump per spec, ducting low along the floor where the heat is needed, dedicated fused circuit. Both CO detectors live before the first light-off. Run the full high-elevation burn-in, then put the $200 clone heater on the spare shelf. A shop that does Espar installs daily is worth paying for this one — the fuel-system work is the least forgiving part.

The locked spec: 16 gal fresh (~133 lb full), ~22 gal grey, every tank inside the box — the underfloor is HV territory with 7.51" of clearance. Fresh forward of the rear axle, low and centered; grey may sit further aft; the rear overhang gets the drain penetration only, never mass. Remco Aquajet ARV pump (no accumulator needed), PEX-A throughout, HepvO waterless traps at every drain — nothing to freeze, nothing to slosh. Plumb the winterization loop now, not in November.

Drain routing around the pack — solved by the BrightDrop builder community and validated by Grounded's production RVs. Four floor-exit corridors the battery doesn't own: the ~6" perimeter strip along the body walls, the patch in front of the rear wheel well, under the cab/jump-seat area (Grounded runs its shower drain forward to a 23-gal grey tank under the driver's-seat floor), and our rear overhang. The routing trick: the shower pan sits on the 2" XPS floor layer with a channel routed in the foam for a low-profile drain running laterally above the metal floor — pan drain position is decoupled from the floor hole, the sink tees into the same run, and the build needs one combined exit hole, total, placed in a 191c-checked corridor confirmed against Math Data. Cluster the wet room and galley on one plumbing wall with the water heater under the sink, lateral to the shower valve — 1–2 ft hot lines, no recirculator, no waiting water down the drain. Thermostatic shower valve, low-flow metal head, smooth-bore flex pipe for the grey run.

Anchor to the Ranger Design 6550-BZL mounting track — the drill-free, purpose-built attachment for this body — with cabinet frames in thin-wall aluminum. Every cabinet is crash mass: tie every carcass to track or bonded cleat, rated for a stop, not for gravity. Weigh sub-assemblies as they go in and log against the frozen budget — this is where the ~120 lb optimism error historically accumulates. The A/C unit sets into its bench bay as that cabinet is built: the bench is framed around it, ducted to the Phase 4 exhaust path, on the 24 V circuit from Phase 7.

The cat is the binding constraint. MarCELL on Verizon (it phones you) as primary, Waggle Pro on AT&T/T-Mobile for carrier diversity, both with internal batteries. Alert on state of charge, not just temperature — wire the power-loss trigger to the house bus. Thermostatic fan circuit on its own isolated supply, so a house-bank fault cannot take ventilation down with it.

• Water: pressure-hold on the fresh side overnight; dye/leak walk on every HepvO joint. No drop, no weep.
• Electrical: full-load inverter test, a real solar harvest day, shore charge through the EMS, 12 V rail under load — numbers must match the design figures.
• Heat: overnight burn at duty cycle, CO detectors live, fuel consumption logged against 0.41 gal/night.
• Pet stack: pull shore power and the main bank breaker; confirm the MarCELL call and Waggle alert both arrive. The phone rings. Actually rings.
• CAT scale, systems in — before final trim. Weigh gate 3. Still under budget with trim + occupants + gear (777 lb) remaining, or trim gets re-scoped now.
• CAT scale, finished and loaded — tanks full, both people, the dog, the cat, the gear. Weigh gate 4. Under 11,000 GVWR and under both GAWRs per axle. This ticket is also Phase 13 paperwork.
• Roof array and rack — put a scheduled visual inspection on the calendar, starting at commissioning. Module faces and backs where they can actually be reached, connectors, wiring and strain relief, mounts and fasteners, corrosion, and any sign of movement. The one owner on this platform with 10,000 miles on an array lost two cells and found them only by looking — nothing at the charge controller flagged it, so controller output does not count as the check. Visible heat damage or a burning odour: stop operating that system, isolate it safely, get it assessed. Do not field-splice around it.
• Shakedown: one week within 100 miles, including two nights off-grid and one DCFC session — the punch list, found near home instead of far from it.

Finish the conversion → weight certificate from the loaded CAT scale → photograph the permanently installed systems → file VTR-61 + VTR-130U (Texas wants 4 of 6 life-support systems permanently installed) → motorhome title issues → then, and only then, RV insurance. An RV policy on a commercial title is a claim denial waiting for its moment. Keep the commercial policy live until the day the RV policy binds.

Consumables and the real failure points, not fantasy spares: heater clone + glow plug + fuel pump, spare MPPT, water pump head, HepvO cartridges, 08115 + sealant, fuses at every rating on board, filters, and the printed one-line diagram taped inside the electrical cabinet. You cannot stockpile a composite body side — that risk is what the Phase 13 insurance is for.