Has anyone tried Grip Clips on a 2-mil or 3-mil poly tarp (dropcloth)? I am prototyping some tarp shapes first with a cheap poly tarp, and it looks like Grip Clips would be the best way to obtain side pullouts. I've tried tying off a smooth object with a clove hitch or constrictor knot, but like someone else noted that method causes a lot of fabric bunch-up.