ive used ripstop nylon,. and rip stop polyester. the same stuff I make my hammocks out of, it used to be commonly available for $1/yd in the walmart clearance bins in the fabric dept. No wrote ups, or threads. cut 2 long pieces, sew them into a square, and add traingular reinforcements on the corners, and ad loops for tie out points. then stretch it out in the back yard and spray it down with the silicone spray. found a few pics, my seam is UGLY.. haha im obviously no seamstress.