Yeah - I've done all the above (insulated tube does okay above 0F.) Around -20F it still freezes and blowing back the water (which I do) ends up "blowing" up the container itself. When I cross-country ski (my cut off temp is -20F) I've given up on the camelback all together and hook my bottle parka up to an old duffle bag shoulder handle and string that around diagonally on the body. I'm just whinning cuz I have to stop to drink =)

Speaking of cold weather and snow - We FINALLY have enough for me to ski as of this morning - course it is supposed to drop down to -50F this weekend...