This is one of those topics that really becomes an individual preference. The mattress arena is tricky cuz as you know, our comfort level differs from one to another. What is good for one may be a bed of nails to someone else. That said, this is what I came up with and its been a good mod.
I have a 2012 Hawk, and the mattress is (was) hard as concrete. Something had to change. I did a fair amount of research on pads, memory foam and plain old foam. Shied away from memory foam cuz I learned that this foam tends to be cold and hardens in cold+ temperatures. Instead of buying a new mattress (foam is expensive) I decided to modify what I had. I took my 4" stock mattress to a place in Sacramento and they sliced 1" off which made the foam actually softer. Cost $5.00 to cut it. Now I have a 3" mattress, still fits (loosely) into the large mattress cover that came with the camper. Softer, but still not enough. So, I picked up a 1" foam "Full" mattress (not memory foam) from Walmart, (they have Queen and King also), but like Bill, we don't pull out the bed slide...my girlfriend and I sleep close and the Full size bed works well for us.
Then I toss a couple of fleece like bed covers as a top/bottom sheets with an optional down comforter on top. This set up is, as comfortable if not more, than the bed in my home.
