Chuck,
When I used mine at Shrewhaven Camp last week I would go back through and tighten the tie down lines a second time (put them on, tighten them, then go around one more time and tighten them again) to get it tied down snug. I didn't put a rug down, but we only had a little snow and it came after I set up the blind.
Randy from Northwoods says he cuts a little pvc pole to set in the blind from ground to center hub in ceiling if leaving out in the winter months to keep the snow from caving it at all.