I thought about this when I first got into this madness. Esp when I read about single layer and double layer hammocks. Heck if you make the lower layer "a box" under your top layer say 2" wide. Basically if you hung the top layer so it was very taunt the lower layer would hang down 2" in a box type form.
[___________________________________] bottom layer
with velcro or zipper to close it off from wind and help keep the heat in?