Here's a follow up to my original post. I ended up purchasing a factory cover from another forum member and then had the it modified so that it didn't hang down so low in the rear. The large rubrail that our boats have makes a great ledge for the draw string to rest against. There's also a couple of straps at the rear that hold it down to the rear tie downs. The cover easily stays on without them, however they make it easier to keep the drawstring in place while putting the cover on. Overall I'm very happy with how it turned out.
The last pic shows a pocket I had added on the side of the cover beside the rear tower leg. This is to put the drawstring ratchet in when removing the cover so it doesn't bash around on the boat while putting the cover on and taking off. With the amount I put the cover on and off, the pocket has been a huge boat saver.
