I found this on youtube.
Not sure if it's a forum member's design or not. I like the idea that it looks easy to rig up and easy to change in the middle of the night if it starts out very warm but the temps drop a lot.
I'm going to be going on a trip in a few weeks and am starting to realize that I'll need some sort of UQ... my last trip was to a much warmer location and even then I had a cold butt. :-)