Didnít try the My Pillow topper, but we did buy a 4Ē memory foam topper from Target (donít recall the brand). It was a regular king size, which was a bit larger than our RV king size mattress. I trimmed the excess with an electric knife.
The topper made a huge difference in comfort. The original mattress was pretty much crap. But, it sleeps great with the topper.
The mattress in our Thor Ace folds over 2' from the bottom to bring the slide in. Has anyone "attempted" a "gel foam mattress topper" and did you get it to fold enough to allow the slide to come all the way in?