Well, with no other ideas I decided to improvise. I got a can of "Great Stuff" expanding foam, made an extention for the application hose, attached it to a wooden rod, and re-foamed the delaminated area from the hole I had cut for the hull access port. The foam is allegedly waterproof. It was a messy job but it appears to have worked. I cut away the excess foam that oozed out after it had hardened and installed the port. The hull is now rigid and the extra foam is quite light. I'll be taking the boat to the beach in August--if I have any problems with the repair I will post them here when I return.