Despite having a warm down bag I often get cold on the side touching the ground, even with my 8mm closed cell mat. I've found a way of producing a 4cm thick sleeping mat that weighs less than 100g and it folds away to the size of a mylar survival bag (about 1/7 the size of the foam mat). It's warmer than the foam mat and gives much greater comfort. email me if you want some more info.