Shouldn't need the floor Jax.  With adequate snow cover it should be fine.  Drill your holes and pack it down.  If you want a floor, both Clam and Eskimo brands make a portables with a floor.  Personally, I don't like the plastic floor because they have the deep channels running lengthwise.  If you could make a foldable wood floor out of plywood, you have a better base- no channels and not as slippery - you can rig it so the wood base is a sled as well.  These things are so well built these days that ventalation isn't a problem either.  The quilted ones hold the heat quite well.  I can just about heat mine with a candle.

Course I spend most of my time in my winter office.  It has wheels.  :)

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