We've been using the mattress as adapted all this year without problems. That means an extended platform and bolster filling the space at the top. Less room at the foot of the bed, but enough to squeeze through. My wife has a wastebasket and a thing for dirty clothes down there, but manages to get past them.
The modifications I considered are explained in post #4, http://www.airforums.com/forums/f42/...ips-47817.html
The plywood extension I bolted on rather than glued and it works fine. The gap at the top was about 3.5" and was more or less filled with the bolster. I cut a piece of 1/4" plywood to fit in the bottom of the bolster—getting the curve right was a challenge, but I used a large piece of butcher paper to make a pattern. A solid bottom to the bolster was important so the fitted sheets would have something to hold onto.
We also checked out organic mattresses and toppers. They are expensive, so we are living with the foam for now. There are a lot of toxicity concerns with the non-organic foam that has been used for years (see post 48 in this thread).
If you extend the bed to fit a standard queen topper, you can use regular fitted sheets instead of the more expensive ones for RV sized beds. We always used standard sheets and they would be so messed up on the short bed that the bed had to be completely re-made everyday; now that's not necessary.