I should mention that I got some excellent ideas (I was too lazy to implement most of them) via private email from Lee Gardner.
Lee added a front hatch to his '92 Express by molding a hatch lid which preserved the line of the deck.
(I feel that I have 'ruined' the looks of my boat to some extent, and if I ever were foolish enough to get in a situation where I had green water surging along the deck, I'm sure I'd find the stuff on the deck would throw a lot of water in my face.....)
One of Lee's very clever methods was using the flotation bag(s) under the deck with Saran wrap and wet glass on top, to press the glass up to the deck underside to form the hatch rim.

Also, I forgot to mention that because of the deck thickness, the actual recess position will be a bit aft of where the mold is made on the top of the deck.