We bought this mattress on Amazon last year and like it a lot. It's a camper Queen "short" at 60 x 75 inches. It's very comfortable and we've since moved it from our old trailer to our be MH. Two things you might want to consider.
I'm 5' 9" and this mattress is just barely long enough for me. But we had a similar bed setup and the wall at the foot of the bed limited how long the mattress could be. This one turned out to be slightly longer than the old one so it made it a bit tight to open the bed for the underneath storage, but I'd did work.
The other thing is this mattress is significantly heavier than the original making it harder to lift the bed to get to the storage. It really needs heavier duty gas lifters.
But the sleeping makes all the difference. The original mattress should have been banned by the Geneca convention