What boots do you like down to 0 degrees? My application will be Elk hunting at about 11,000' in Colorado mid-October. I have backpacking boots I have used for years that are good for backpacking, but I realize my feet get cold in these when I'm sitting still at a mere 20 degrees above zero (thin polypropolene liner with heavy wool socks over), thus they probably won't cut it if it gets cold and I'm still for some time.