I'm not entirely sure which forum this belongs in, but hopefully some of the more experienced folks here can help me out. My problem is that it is virtually impossible for me to sleep in any position but on my stomach, arms folded under my head. In my youth, I could sleep anywhere in almost any position, but as I age I find I have far less tolerance.

Given this restriction, I find that I have a very difficult time staying warm in alpine conditions, or in shoulder season. It seems like all sleeping gear is designed solely for flat-on-your-back sleeping. About the only thing I've come up with that helps at all is to wear most of my heavy upper-body clothing layers so I can stick shoulders and above out of the bag. This is less than ideal.

I can't be the first person ever to have this problem, can I?

What have other folks done to improve colder-weather stomach sleeping, where the mummy bag concept just doesn't work?