When in Quartzsite two years ago we bought a new King mattress. It is thicker at 14", a couple inches thicker than the mattress it replaced, and it has several layers made from varying types of materials. The top layer is a memory foam material with an egg-carton look. This mattress is the most comfortable one I have ever slept on, and my house mattress is a nice warm waterbed. I remember one alteration that had to be made, that being it had to be altered to be 3" shorter so that when the slide was retracted the mattress would not press on the drawers too hard. Even at 3" shorter it still presses on the drawers, but the vendor seemed to know from experience that the mattress was too long for motorhomes and had to be altered to allow the slide to fully retract.
It was expensive at about $1,300 including pillows, but Leslie gets pretty much what she wants. We have that type of arrangement. Don't most of us?