I need advice on options to replace the old foam mattress on my 88 Coleman Colorado. I'v camped twice on this, first a few day trip which had me hunched over in pain for a week or better (putting off back surgery since 95).. the second time a quick overnighter with a featherbed mattress topper added. The topper made a difference, but not enough. I was under the impression I had a full size mattress, and could simply replace with an air mattress which prolonged my tenting days nicely. Yesterday I actually measured the space and found I have 45"x70". The idea for air was to be able to deflate a major portion of the mattress or bed height with added bed topper. This is important on my pup as too thick a bedding setup holds my canvas bows up, and makes the vinyl cover tight and difficult to keep corners covered. My pup is all canvas/vinyl, no wooden flat roof. Pictures can be found in my signature. I'm wondering if the typical air mattress in a length of 75" will conform around bows at corners of my slideout. Or perhaps there is a 3 or 4" memory foam available I could trip to size, but also keep my hips from bottoming out.. but I weigh in at 250lbs currently. I'm working on that.. I'd appreciate any advice y'all could provide for possible solutions. Here's a few pics of my space..