Oh and Tom, if it was me, I would get the -25. But that is just me. I haven't camped in your location in winter before. Right now I have a bag rated to -25, but it is a cheap one, and I picked warm and cheap, not light for the two out of three choices you get with a sleeping bag. It is a little over 8 lbs and probably stuffs to around 50 liters. It is not a problem right now because it fits on my sled and my dog has no problem pulling it. But I would want a more compact one in the future. Although I don't have money for one right now, I am trying to decide how I want to replace it. I think I might end up with a down WM 20F bag and a synthetic outer bag for winter only. Maybe a Wiggy's outer.

Sorry, I don't think I helped you at all.