I didn't see anything about the type of hatch you're using on your site. What brand is it? VCP and Kajak Sport hatch rims can be bonded with epoxy. It's a good idea to bond them in place, then add a layer of 'glass overlapping the rim and the underside of the deck. I did this when installing a day hatch in a 'glass boat and I can sit on it without any creaking or cracking sounds.