[QUOTE=One thing I've heard about, but never actually heard anyone with personal experience about, is being warm into the 20s w/o a pad or underquilt. Clark says you can use the insulation that's already there, and maybe some inflated sandwich bags, down to 20 or so. Never heard of anyone actually doing it, though. And I'm very skeptical.[/QUOTE]
I think on one of the other threads on new log temp I posted about doing just what you talked about. I was hanging in the loft of a shelter that night so the wind was limited. I used a number of inflateable ziplock bags and as I went to bed that night the Temp was 9 degrees according to the little therm. that I have strapped to my pack. I think two of the pockets were also stuffed with gear like sleeping pad and bag stuff sacks etc. The only other insulation other than the clothes that I wore that night was my inflateable sleeping pad. I woke up several times through the night but more as a result of too much to drink before bed than being cold. I was too cold to get up and take care of business and was warm so fell back asleep quickly enough until 6:00 am or so when it was go time both figuratively and littearly.