Like you the RTT and even our KK mattress was just too darn hard/firm for us. For our then Overland RTT, our then Maggiolina RTT and now our Kimberley Kamper we had a local mattress manufacturer (small two man shop), Reno Mattress, make us mattresses that were/are worth it to us. No regrets.
Before moving on to a custom mattress we tried memory foam but its best if temps are above about 65*F. We tried one in the Overland the weekend we happened to be at Coyote Flats, SW of Bishop CA, when the temps dropped into the upper teens; it turned literally brick hard. Let's just say we didn't do that again 
For the trips when its just me, my dog Sieg and the Land Cruiser without KK in tow, I use an Exped DAM 9 (Down Air Mattress) and its da bomb. Plush, quick to inflate (especially with my OBA) and compact when its travel time.
Oh yeah...five ten and two bills.
Last edited by spressomon; 07-08-2011 at 11:51 PM.
1999 Toyota 100-Series Land Cruiser...not nearly stock
2009 Kimberly Sports RV 'King of the Offroad' trailer: Sadly gone but it sponsored some of the best memories of anything I've ever owned!