I say forget zippers, forget snaps. Both these systems die early and often. Go visit the "sailrite" web site and look at the "common sense fasteners". Figure a way to use them for your application and then forget about early failures! My Triumph sports car used both these fasteners AND snaps on the convertible top. It also had a zipper on the inside. All the snaps failed, the zipper failed, but the 'common sense' fasteners were flawless for the entire time I owned the car. Eric Thompson S/V Procrastinator South San Francisco capteric36@sbcglobal.net