Hanging your tarp from each end is fine. However, I do add a loop of shock cord to one end (just like your tie-outs) for nylon tarps. The tarp will stretch when wet and will sag along the top, too. The shock cord also adds some shock absorber to the system for gusty winds. I use 12 inches of 1/8" shockcord tied into a loop with a double fisherman's knot.