The big problem with trying to replace the typical mattress is it is so thin it is difficult to get anything that will still fit when folded up that feels anything better than the one that came with it. We ended up buying a double air mattress from JC Whitney for about $30. Works great, is not heavy, packs up small when deflated, quick to inflate. If we have someone with us for several nights, we throw it up on the big front bed during the day. Blows up real quick with a 12v powered inflator.
2003 Dodge HO 6 speed Laramie Dually, Jordan controller, RDS fuel tank, Air Ride 25K hitch
Carriage 36' fiver, Onan 6500, Prosine 2K inverter, 3 slides, MORyde IS and Kingpin