Here's a few shots of camping last weekend.
Showing an air mattress from Costco for $45... came with a 12V pump takes 4 D cells. Didn't pump the mattress completely full, so it squishes around the wheel wells. With two adults on it, the pressure builds up and provides good support. The mattress did not squirt out of position and just stayed wedged in there between the wheels.
I made a cardboard "ramp" that fills the difference in height gap created behind the folded seats and trunk floor. The ramp is cardboard folded around and around in layers of successively longer spans, ending up with dimensions 3" high tapering down to zero over a 21" distance that is long enough but not so long as to obscure the removable trunk deck lid over the deeper trunk. The width of the ramp is 38" to fit between the wheel wells perfectly snug. Being under the mattress, it does not get crushed, is lightweight, and to transport it I just flip it up and keep it behind the seats when they're in the upright position.
Slid the front seats nearly all the way forward. Put two 69L Rubbermaid containers with lids on the rear seat floors to fill the void, and rest mattress on top of those. Worked perfect. These are $10 each.
Other photos show the adapter I made to go from from TT-30 "RV" outlet (120VAC 30AMP) to NEMA 14-50. Have to dial down the amps to 24A. Filled me to 90% overnight, perfect. In the morning I did an experiment "go until you blow" to see how much I could pull from the TT-30 outlet. It let me pull a full 30A for several minutes maintaining 120V without dropping voltage... so I probably could have cheated all night but didn't want to risk popping the breaker and losing out completely on a charge.
Super nice just hitting the heater on whenever temps dropped too much... We learned the best way to do this is just leave the climate controls on and set the way you want, then open and shut the rear door. It runs for half an hour then stops.
We made window covers from stiff box board, cut to shape (traced from windows with doors open) for privacy on the sides, and used a traditional front windshield sun protector for that and just left the rear glass an pano glass unblocked.