I'll second the use of the sit pad under the hip. I use the sit pad initially in my vestibule, so I can kneel as I enter my tent, and keep the inside of the tent clean. I use a standard Klymit green inflatable, if I find my hip is digging into the cold ground, I'll grab that sit pad, knock any loose dirt off it, and stuff it under. I've also been known to use spare clothing underneath the air mattress to level one side of the mattress when I had to pitch on a slight incline, this also helps with the cold.
I've also found that the more I hike, the more weight I lose, the less my acid reflux acts up, and the more sleep positions I'm capable of sleeping in. Especially after a 10 hour day of hiking. I found testing sleep pads on the living room floor at home to be pointless. After a non hiking day, I'm not nearly tired enough to fall asleep on a thin little mattress. Works fine on the trail of course.