Heres a decent trick if you want to keep the hatch as well. Before you do anything to the hatch, wipe some vaseline on the hatch and the surrounding area. Take some regular Autobody putty, mix it up and apply it to the hatch and surrounding area. Let it harden, then flick the finished mold off with a finger nail. Once you have made the opening, you can take the mold and lay a thin layer of epoxy into it. Once that hardens you can add interior stringers and frames, latch mechanisms, etc. then very gently pop it off the mold. Theres your replacement hatch.
Sabre