Back to the question of clothes in the sleeping bag: Just a note that the EU's EN13537 ratings assume the sleeper (a test dummy) is wearing a base layer and a knit hat inside the bag. For 10-20* F bags, they also assume a sleeping pad with an R value of 5 (warmer than most 3-season pads). Of course most of us are not "average," and hopefully none of us are dummies!