Our 2011 Outback "329" has a short Queen mattress. We placed a thin egg crate sponge topper for comfort as we did in our previous RV. Standard queen padded mattress cover as the final topper.
In our 2005 Hornet TT, we bought a custom short queen mattress for $450 and it was GREAT.... (still used the thin sponge topper),
Prior to RV'ing had 2 boats with sleeping "aft cabins". Similar platform beds. All needed some type of comfort additions to preference. We are not large people. I am pretty sure size (length or weight or both) adds complexity to finding the ideal comfort.
I know right now; when in the RV I do not yearn for my bed at home. That's a good indicator of comfort.