Hmm-

My pack cover is not big enough to cover the underside of my hammock. Any under-hammock system will need to be kept close to the hammock, either snug or at least the edges pulled tightly against the hammock to seal warm air in and drafts out. There is a small-diameter elastic cord sold in small packages at places like Walmart. I use this, doubled, to hold my space blanket against the hammock, along with connecting the side tie-outs to the blanket with small sections of the round elastic cord. The elastic and space blanket together cost under $4, usually. Make a casing (tunnel) on the two long ends by folding a couple of inches over and taping them down. I use flexible duct tape for this. (I found it at Lowe's.) It looks a lot like thicker mylar, but sticky on one side.

CamperMom