Gossamer Gear’s Sitlight Pads are just great for this if you cut them in half lengthwise. They can be still used in your pack’s pad sleeve but when it comes time to make your bed, either on the ground or in your hammock, these little fellows will keep your elbows and shoulders toasty warm.
You lay them egg-crate side down to get maximum insulation. The egg-carton shape makes them effectively 2 cm or nearly an inch of foam, and all those little hills and hollows makes them ‘stick’ to your groundsheet or hammock so they don’t move around.
There are three sizes available now. Mine don’t seem to be any of those. Mine are 9 ¾ x 18 ¾ ( 25 x 48 cm) and weigh 34.5 grams. This is a pretty small weight penalty for the comfort they bring – and they still do double duty as a pack frame and a trail seat! Mine are also used as my dog’s mattresses, but you pretty much need to have a JR (as you should) if this is going to work for you.