Do you have the vent or fan above the bed? While taking apart the vent to replace the broken arm for the vent cover, I saw it was pre wired for a fan. You could use that as a power source.
In my GX470 , I ran a G34 starter and G35 house both Odyssey . These were separated via a Bluesea ACR. I mounted a Victron 75/15 MPPT under the hood, and carried a folding 100w Renogy panel. Nice thing about the ACR set up was that once the house battery was above 12.7(or close to that) via...