I hunted first rifle in Colorado this year because I had conflicts during archery season and it was very cold. Down around 0 and I froze in my new Big Agnes Blackburn UL 0 degree bag with insulated pad. I ended up wearing pretty much every item of clothing I had and was still cold. Anyone have a suggestion for a good bag for backpack hunting when the temps get down to 0? I've been looking at the NF and Marmot in a -20.