I tried a different approach this year, and it improved, but not perfected my sleep. The biggest improvement was using a Neo Stratoloft sleeping bag, which awesome fore side sleepers. If is roomier, plenty warm, and has a pocket/hood to hold my pillows. It also has a pocket in the bottom for your sleeping bag and 2 bag can be zipped together. This bag lone increased my comfort tremendously. I used a 2" Thermarest on top of the Pilbara hard as a rock mattress. I have considered pulling the mattress out and just keeping the Cabelas Ultimate pad in there, and using the Thermarest on top of it. I was unable to close the tent with my sleeping pad on top of my mattress (deflated) but think it might work if I used the Ultimate instead of a mattress. I think Josh nailed it - most of the RTT mattresses are brutal for side sleepers.
As a side note, it was pretty cold when I camped at Yellowstone but the tent and my Nemo bag kept me pretty toasty. I was hoping it would snow a bit more so I could test its snow-storm worthiness, but probably only got an inch.