Anyone out there use tunnel bags? I wear a backpack but been thinking about getting a good tunnel bag and not wearing the backpack anymore. Just wondering which ones people have tried and like and were water proof, zippers worked, things like that. I would like one big enough to put one of my layers in plus my snobunje, and possible my shovel. I know that sounds like a lot but I would think a n ice tunnel bag could handle all this and maybe have room to spare.