I made an under quilt using a combination of these plans for the hammock and tarp I made this fall using instructions here.
The local rental place moves lots of TVs this time of year and they saved the insulation for me. Most of the sheets were long and wide enough. I used packing tape to piece together those that weren't.
It's a 70-inch x 42-inch 3-layer UQ with ripstop from Joann's on top and bottom. It rolls up as small as the others in this thread and works great. It weighs 16 ounces with the shock cord.
I've used it for a nap, but not overnight yet. It's very warm. I'll get a picture soon of all three.
Thanks for the help!