In reply to needvert:
id look into some of those curved-cut designs the little US companies are doing. what you gain in footprint will be offset with less flapping material. some awesome stuff coming out of that scene right now - if you can get hold of it.
id go larger than smaller personally, then you can seal down the edges with rocks/snow when the weather is truely shit, along with just getting the edges closer to the ground in general but leaving useable space.
whatever you get, trry and avoid ones where the guy loops are non-water absorbent otherwise they become an issue.
