Consider the risk I am taking this weekend...
My 11 yr old daughter, Thing1, and her friend, Thing2, will follow me into the woods, where the forecast calls for snow, sleet and freezing rain. Thing1's mother is certain that her daughter will be sick next week, and is worried that Thing2's mother will be seriously upset if her daughter gets sick.
I told my wife not to worry, because I will make their underquilts today. What I did not tell her is that the first time anyone will use these underquilts will be when Thing1 and Thing2 hang on Friday night, in temps that are supposed to dip into the 20s!
The 3' X 5' Warm Thing Quilt consists of one yard of Wiggys Window Covering, one yard of Insultex, one yard of lightweight, red nylon fabric, and 16 feet of lightweight 2" nylon webbing. All I did was cut, layer and bind. It weighs 2.2 lbs, and has less than $20 worth of material in it. Now I will add loops at the corners.
I'm also going to make Insultex half-bags, like MrPrez described. In case the Things get cold, I have pads.
Of course, I will be sleeping in my PeaPod.