I'm with those recommending a replacement vs. repair. A good cover is worth every penny. I'm convinced most structural rot comes from a leaky, or no cover. I shake my head each time I see a nice looking boat stored in the open, wide open.
I keep my boat outside in the winter in IA. I do use woven plastic tarp over the mooring cover secured w/bungees. I have snap-in vents in the mooring cover, and place PVC 'J' tubes over the gunwales just in front of the rear seat backs for extra ventilation.
Heavy snow build up is a yearly problem. So I have three lines stretched from the bow cleat over the windshield. One center, two going to the corner rear cleats. I use my throwable and towels to keep the lines from biting into the sundeck. Then four adjustable tent poles. Three in the cockpit, one on center in the open bow. Dryer sheets scattered to keep the mice out.
No problems with mold in the spring, after 22 springs.