i went to a local upholstery store and bought a piece of white foam (i forget the specs) 4" thick and memory foam 2" thick....
i havent bought the covering for it yet so i have it wrapped in a few sheets. its just a bit smaller (they cut it for me) than a twin mattress and lays across the bed platform in the back of my van.
it is incredibly comfortable and i am into it only $140.
i sleep better than i did in my apartment with an expensive queen mattress.
no pressure points at all....ive never experienced that, contours to my shape just right. im a big guy >300lbs.
i was looking at froli sleep system like acrete did but i dont think i need it with this configuration at all.
i found a website that will make a cover for me here http://www.slipcovershop.com/index.asp