If you want to take a boat like yours that is built for coastal at most to Hawaii the strongest solution would be to glass the bulkhead in and attach the chainplates to them or place the chainplates outboard on the hull and lose a bit of pointing ability. Nothing else you can do will be as strong.
I appreciate Your input on this so please correct me if i'm off but Why is attaching them outboard on the hull different from the cabin top with a wire strut attached to the molded interior(where the bulkhead was attached) or to what the compression post sits on. I think the cabin top is the same thickness as the hull, being built in the late sixties when epoxy was cheaper and they didnt know how thick or thick to make them, I think its the previous
owner adding wood and glassing on top too. if the deck to hull joints are good. Have you heard of George Benson he cruises all around in a rebuilt Coronado 25. what about contessa 26