The hard part here is the fold in the middle.
We have a respected local custom mattress shop that says they will make any size. When it is time to replace, I am thinking about giving them the business so I can get a folding mattress with high end foam layers. Then again, I've seen the price of their regular mattresses, so it probably won't be a cheap solution.
I figure I can go about an inch to an inch and a half deeper (2-3" folded) within the space available when the bunks are folded.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2018 Nissan Titan Midnight Ed.