After allot of searching I found the perfect insulation. Joann fabrics had 1/2 inch thick polyester bat insulation. It weighs only 4 oz. per yard 48 inches wide. I am going to sandwich this between nylon ripstop outer layer and Mylar space blanket top. The mylar will be against hammock bottom. Inside I am using a wide custom cut Gossamer Gear 1/4 thick evosote pad. I will take some pics during construction and post later. total underliner weight should come in around 12 OZ. If real cold out I plan to layer my down vest and extra clothes between hammock bottom for extra insulation! I will let ya know how it works out in testing. Best part about the insulation it is onsale fifty percent off. Only 9 bucks for enough for two underliners! 3 bucks for space blanket , free ripstop. couple bucks for elastic cord . grand total under ten bucks per hammock!