Add a Layer of Fiberglass Resin to the inside, glue some fiberglass cloth onto that resin, add another layer of resin on top of that fiberglass, sand off any jaggies.
After the sanding, make sure no dust is on the inside, that stuff will kill.
And everyone, just answer his question, not everyone reads the stickies, if everyone did, there would be no use for us, lol.