Huh? How would throwing an air mattress in there give you any kind even remotely level surface to sleep on? Not only would you be sleeping with the existing elevation change somewhere under your hip or legs, there is the void where your head would be (where rear passenger legs would go).An air matress would just sag & not support my head & chest. I am 6'-1" and to sleep in there at that height you need to max the space beyond the existing floor bed you get with the rear seats out flat- if you look at the fold out section, that is extending the truck bed to max the length with front seats fully pushed forward. On top of it, you can put anything you want- air mattress foamies, whatever. Someone show me if I'm wrong, but I cant see how just throwing an air mattress in there is gonna give me a flat sleeping surface, with the rear door closed, unless i'm say 4'-6" tall?? With this setup, my feet just touch the rear door closed.
