Spidey, thanks for the info. Unfortunately having never built a boat and having to wait a few days before my supplies even get to me, I have little idea what you are talking about. I am sure it will all be more clear when I get to that stage or at least have some materials in front of me. I was thinking the easiest thing to do would be to lay a couple of sheets of wax paper over the finished hull and make a fiberglass mold. I could then pick this up and cut my hatch. Then lay my clear mold back on the deck and trace the hatch opening. After that I could just flip the mold over and proceed with the vaclav method. The only problem is this is an extra stage and I am very lazy. (I don't think that the mold being 4 mm off, as it is on top of the deck, on a radius of many meters would matter all that much) I will keep your letter and look at again soon. All advice is much appreciated. Thanks, Todd