Randy that is the method I use. I cut the hatch out first and use clear packing tape on the top to tape it back in place. Underneath I make 4 lines across the so I can use them to line the fiberglass mold to the hull after I create it. I use overlapping packing tape to create a release surface. Then I cut thin strips of pink foam to create the bump for the recess but you could use weather stripping. I cut it just thinner than weather stripping so when it is replaced with weather stripping it can be compressed and still allow the hatch cover to align with the deck. I just glue it onto the surface of the tape with contact cement I fiberglass over it and when the glass is partially cured I draw lines on the glass on top of the lines I have drawn on the hull so I can align it again when after I pop it off. I pop it off before it has completely cured, trim it on both sides and epoxy it in place with thickened epoxy. I just use clamps to hold it in place when drying. Really a lot easier than it sounds.