i can't speak for the thermal blanket, but if i were going to shelter in a hammock in temperatures that would require insulation, i would go with a mummy type sleeping bag. bulky yes, fairly lightweight, and seems ideally shaped for a hammock. i own a 30F mummy bag from coleman that i rather like. i've had it for years and it shows no signs of damage, though i haven't exactly abused it either. i haven't tried any other bags, but i'm sure others will give their own recommendations.