I've thought of using trash bags for insulation under my hammock. They are good to stand on when getting out of the hammock. I only carry one though. It's rather large and made for a 45gal. can. If I cut it open on both sides it would make a smallish tarp. I like to keep it whole as long as it will last though. When using them for picking up leaves in the yard, I can fill it to the point that it's to heavy to carry.
I was going to use a space blanket fastened under my hammock for an insulation pocket but I think I'll sew some fabric for that.