I have pondered this conundrum too.

My suggestion is not to use the method suggested by CLC. What I plan to do with any future S&G is to lay on some cedar strips over the hatch areas to get the right curve, before, or perhaps after, cutting out the holes, gluing and glassing them up, then cutting them to fit the holes. I think a better seal and a more attractive result will be obtained, especially since I usually do a strip feature on the cockpit (See picture) as well.

Et