Trying to keep my feet warm in the Midwest winter hunt. I sit 18ft up the tree facing the sw just inside the wood line overlooking a narrow creek. Typically if there is a wind it will come in from the nnw. I wear a thin black dress sock against the skin with a heavy wool sock next inside of a 1000g thinsulate Irish setter hunting boot. Temps usually hover around 15 to 25 during the cold weather hunt. My feet still get cold after about 3 hours in the tree. Any suggestions to keep them warm? All the rest of my body is plenty warm.