I don't think your going to be able to repair that by glassing though a couple of ports. If I was going to even try that repair I would do it by cutting a hole or slot in the inside hull large enough to actually be able to work on it. I notice the foam blocks there so they would have to be removed to do the work.

The other thing's I would consider would be pulling the cap, making the repairs and reinstalling it or glue it together good enough to make a mold of the deck and then make your own part.

If you are able to fix this hull you might want to add a small port to the other side and glass the deck to the hull in that area. Good luck.