CBergstrom, here's my plan for the floor:
I had the same issue with my zero gravity chairs. Everything went on top of them to the point I begrudgingly would get then out.
Here are really crappy pics of the ceiling:
Looking from the inside out, it's about 7" difference from the hatch door to the ceiling:
I have a drain pipe about 24" off the wall of the basement (closing off the space under the stairs) about 40" back from the hatch opening/camper side:
The hatch opening is about 24" tall by 46" wide (using my 2' level as a measuring stick).
And, here's the mess I'm trying to tame: