In the past, I've used the damaged sections to piece together and shape a repair patch.
http://www.teamseacats.com/2008/02/19/a-crushing-defeat/http://www.teamseacats.com/2008/03/03/fiberglass-repair-by-airmail/It sounds like it may be a bit late for this method. I would probably find a similar section of hull to build a quick and dirty mold from. I would layup the outer skin and then build it inward. I'm not sure what I would use for the foam core, but I would probably try to source some real foam core used in boat building and of the same thickness as in your hull (someone has to have a scrap piece). It can be heated and bent to shape probably with a heat gun over the back of the skin piece in the mold. Once shaped, glue that to the skin with epoxy/microballoons. then build an interior skin to that pices. With that done, cut the patch piece to fit your hole and use the wood stick method (in those links above) to get the patch to fit. Then taper the seam back so you can build glass from the inside out in a thin area around the seam. Fair, and finish.
