For what ever reason I couldn't answer you post in the thread you posted it in. I'v used a Mr. Heater Buddy heater in a Blind in Sask. to -20 C and it was very helpful in allowing me to stay out there all day. To me one of the most important thing's to be able to stay out there all day is keeping your feet from getting cold, I use a thick, dense rubber foam insulation to rest my feet on to get them off the frozen ground. I also use the insulated boots from Arctic Shield, their like an over shoe boot, you put them on over your hunting boots, I find they really work well. A buddy of mine has one of those Heater Body Suit's and swears by it.