Magic Fairy dust. Just kidding. 2 straps of Gorilla tape. And I put a T-shirt under the glass rotating plate to keep it from rattling going down the road. Hurst
I know our truck is designed to disable lights and accessories when the battery gets to 11.6 volts. I wonder if you could find the low voltage shutoff circuit and tie in a 300 amp relay from that to your inverter to prevent it from draining your battery fully.
2016 Cascadia. Cabinet has many bolts to remove. I left the bottom piece for miscellaneous storage and because it has one of the AC ducts attached for the APU. Under fridge is one of those interlocking cushion squares (Harbor Freight is cheapest) I drilled a hole on each side and installed eyebolts. Then a simple one inch ratchet strap holds it all down. Note: I-75 in Michigan did work this setup loose one time. Luckily we don’t go up there much. Occasionally it needs readjusted. Our new Cascadias don’t have the cabinet behind passenger seat.
I think the problem is that they're set too low, so there's still not enough juice for the starter to crank. This is the case with my inverter anyway. If it shuts off from low voltage, it's already too late.