The same insulation you use on the ground works fine. Don't know why you are pretending otherwise. I have use the same pads in a hammock without issues, as long as you have clothes or a short pad to block convection where your arms inevitably leave the narrow pad in the sprawly - good comfort of a nice wide hammock. A wide pad from gossamer gear works to the 40s without extra measures but another pad is needed when it is colder, since those pads are thin and would have the same r value on the ground - around 1.5 at best.