lots of responses - nothing constructive
would have to say they have not had much midwinter shelter use - blowing snow etc does make just a sleeping bag less than ideal
a much overlooked option is the bivy sack - reasonable weights, takes up no extra room, keeps the sleep system together, adds warmth, and can be used outside the shelters
example:
http://www.outdoorresearch.com/en/ca...category/2158/
dominating space in a shelter is never nice, even just being spread out in a sparsely used shelter, be ready to consolidate for later arrivals