Would depend somewhat on what scale the model is but you're going to have trouble getting it to conform to any curve unless the G10 is very thin. Even then, you would need to laminate it with something (G10, ply, etc) to try to get it to hold its shape. In any case, its probably easier to mark the hatch on the surface, cover the area with saran wrap, packing tape, or backing from iron-on covering, and lay up several (slightly oversized) thicknesses of fiberglass cloth (10-15 oz/sq in total) and epoxy laminating resin. The result will conform exactly to the shape you need. When cured, you can cut/sand it down to fit. Most hobby stores sell 1 sq yd packages of fiberglass cloth. If you don't have epoxy laminating resin, you can probably get by with 30 min epoxy thinned with acetone or denatured alcohol in a pinch.