I've not found a RV matress yet that was to my liking. The Serta's that are normal home thickness seem hard. Our little TT came with a little thin matress that is about 3" think and just slightly softer than the plywood it lays on. We bout a 3" memory foam pad from Sam's club and put on top of it and used it all last year. Was so comfortable, we took the memory foam pad out of the camper after we finished last year and moved it to our home bed.
Last weekend, I went and bought two more, one for the camper bed and one to slice in half for the two bunks in the rear my daughter and her friends use. Now we all will sleep in comfort.
These ran about $100 each and for us, were money well spent. They don't get hot, they relief the pressure point pain we were waking with prior to having them and we are sold on them.
2015 GMC 2500 Denali Crewcab 4x4
2019 Forest River Wolfpack 23pack15
Hope your travels are safe and the friendships made camping are lasting.