No matter what time of year I use a hammock I have always found that I lose a lot of heat from the underside of the hammock. Any insulation that lies between your body and hammock gets compressed and therefore becomes compromised.
Normal camping convention is to use a barrier between you and the floor to prevent heat being conducted away. This usually entails using a pad such as a Thermarest or a foam roll mat. Neither of these are a great option for in a hammock. I have always found that during the night the pad moves and you end up with a cold back.
The solution is to suspend your insulation under the hammock so it does not get compressed. Such systems are given the term under quilt.
After trying to get hold of a hammock under quilt (UQ) in the UK without success I decided to make one. Two years later I think I may have made 50 or 60 under quilts. My UQs are made from pertex with at least a 800 EU fill down filling.
Tabs and suspension points are added to ensure that you can customise the fit to a wide range of different hammock designs. This includes the excellent Warbonnet Blackbird and Hennessy Hammock range.