Here's a pic of what I am considering. The corners are rounded with a 3 inch circle and the sides follow the feature line 3/8 inch in on either side. The cover for the forward hatch measures 12" x 9" (approximately, it's not really rectangular) With a 3/4 inch lip the opening will 10 1/2" by 7 1/2". The piece of tape indicates the bulkhead location. Since I took this pic I've moved the hatch location back a little so my cut lines will be across the staple holes. The rear hatch is similar and measures approx 13"x 11".

Dan