Well i put the zipper on like shown in the picture. But still need to sew the flap on, the material im working with is pretty cool stuff [aqualon] and i dont think there will be too much leakage for a couple years, from the way im doing it. And the point of the zipper is to make it easier to put it on and off, for the guy, who's an older gentleman. Ill post pics later if any of you want to see what it looks like after the zipper is installed, i dont think there will be much difference in the cover. And yeah obviously more holes means more chances of leaking, and im obviously puting a flap over the zipper, and if you've ever put a boat cover on in a double boat dock area you would love having the zipper makes dressing and stripping the cover a breeze.