We recently moved into a brand new residential 5th wheel full-time. We quickly noticed the mattress sagging on both sides with a hump in the middle. After 9 months, I was waking with lots of aches and pains. We had previously purchased this mattress in a queen size for our recreational 5th wheel, and absolutely loved it. So we were thrilled to discover the same mattress in king size for RV's.
I urge you to consider this mattress, because while it is the length of a standard king size, it is 4" narrower . Our friends bought a standard for their 5th wheel and say it's very tight once you add the bedding.
Sleep is improved, waking without stiffness or aches and pains. Love, love, love this mattress!