I am trying to put together a bag. The issue I am having is trying to figure out the best shelter options for a typical Finnish winter. Last year it was -30c here. Obviously I don't want to be carrying around a great big lump of a sleeping bag and I normally don't like to part with too much of my money. Any ideas on a good setup? I was thinking along the lines of a wool blanket and bivvy. Anyone have any experience of camping out in those types of temperatures?