I use tie downs, and have not had trouble with wind. I always tip one side, but a couple of years ago, that didn't stop the water from pooling during a huge gully-washer (I was actually sitting under it reading a book when I noticed the bulge). I also tried to lower one side slowly only to have it yanked out of my hands. Mine is now bowed, but I found it advantageous - I don't unroll the last 6 inches, and while I still tip one side, it can't accumulate because of the bow shape.
I have too much setup outside to bring it in at night.
