I've mentioned this in several other posts, but I'll say it again: After reading several mattress posts, here, I went out and bought a 3" memory foam topper for my (non-pillow-top) Denver mattress even before I ever slept on it. After 3 nights, I kept rolling into the "depression" my body left in the memory foam. Then I read a post where the poster said they put the memory foam topper underneath
the mattress - like a box spring. I did that, then added a 1" corrugated foam mattress topper (left over from my old camper) on top of the mattress to make it a "pillow top".
This combination is the most comfortable mattress I've ever slept on!
I contend the reason the mattress in your trailer/MH/FW is not very comfortable, is because it's setting on top of plywood. So, if you've invested in a memory foam topper and don't like the result, try putting it under
the mattress. I think you'll like the result. I sure do!