For padding the corners, I've tried bubble wrap with duct tape, styrofoam corners with duct tape, and old towels with duct tape. I got tired of having to spend a couple of hours every summer cleaning off the residue from the duct tape. Now I use styrofoam corners and tie them onto the TM with twist tie
http://www.neeps.com/288498.html?productid=288498. So far, all the corners have stayed put even on very windy days, I can re-use the twist tie over and over, and it doesn't rust. It's amazing how many things you can find on the TM to tie onto.
Works for me.