Clois,
When I worked on my body, I learned to extend or patch a hole, the best joint was a "scarf joint" where it tapered back, on both sides, on a ratio of about 12:1 That means your edge would be tapered to a knife edge, with the sharpest point being the middle of the material. If the panel is 1/4" thick, then both sides would be tapered back about 12/8 or 1 1/2". Then the layers are built up individually, to the new edge that you want and extending the glass in subsequent layers over the old edge. Ideally, you want multiple layers of glass layed on top of one another and gently overlapping each other as they climb the taper of the scarf joint.
This is a good link to
Glass/Composite repair on the Fiberglast site
if done this way, the joint is as strong as the original material. Make sure you properly identify the material you are patching: is it polyester resin, vinylester resin or epoxy and use the proper material for patching it.
Fiberglast is a good source of materials, in case you weren't aware
Paul