but maybe you could stick it inside your sleeping bag instead of under it?
Thermarest prolite with a silk liner slipped over it for luxury. On cold nights with long johns on use the silk liner as designed as the longies keep you off the pad. My first 100 or so nights in my HH was this way, the last 50 have been with JRB quilts and they both work well but the quilt is better, whether it's $500 better is still up in the air. I liked having the pad along incase I had to go to ground which hasn't happenned yet.