My 2013 Eagle 266RKS has the standard Denver Mattress (they didn't start putting the pillow-top in until the 2014 models). After reading so many complaints/recommendations, I added a 3" memory foam mattress topper. I didn't care for it at all! Too firm, initially, then formed a dip where I was laying that made it impossible to turn onto my side, or even change positions. I took the advise of a couple of folks here, and laid the memory foam on the plywood (like a box spring) and put the Denver Mattress on top. Just for grins, I added a 1" corrugated foam rubber mattress pad (left over from my old trailer) on top of that. Now, it feels just like my Simmons Beauty-Rest Pillow-top at home. It's firm, but not hard - with just a little "cush" on top.
Mind you, I haven't actually slept
on it yet - only laid on it and sat on it. I'll be giving it the official test sleep in 3 weeks, when I start my "full time" camping adventure. I'll report back after a week or so . . . if I can drag myself out of bed (lol).
While I was at it, I moved the bed struts 4" toward the foot of the bed. The change of "leverage point" does a much better job of supporting the additional weight of the memory foam, pad, linens & blanket. And I didn't have to spend $50 for new struts!