I'd just make sure you do a through job of injecting resin and be done with it. Laying glass on the inside of the deck is going to be a tough job. And unless you're able to do a good job of it, it probably won't add much strength. You'll have to flip the boat over to lay in the glass and get it to stay. This means you'll be reaching in from under the boat and trying to work through a 5" or 6" hole and you'll only be able to lay glass as far as you can reach inside.

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