My concern is, would there be any significant weakening of the hull by going with larger 'rectangular' windows than the small elliptical fixed lights that are in there currently. Anyone think I should be concerned on this matter???
Oh, yes, very much. Anything much larger would offer structural issues to the hull, but Ed might be right about the ports themselves. There are a few observations:
1. Enlarging the existing ones wouldn't give you that much more light.
2. Opening ports in a hull? I originally thought: What are you thinking? Then I thought about the Titanic, but, really, sorry about that. For your production boat, or for any boat of that size, what you REALLY need to research is not simply a few manufacturers of portlights, but ones that are used by major boatbuilders that DO install opening ports in the hull. Try Hinckley. I doubt if Morris Yachts does, but maybe.
3. Given #1 and the possibilities of leaks, can you investigate more opening portlights that will always be ABOVE the waterline?
Good luck, would be interesting to know what you learn.
Don't go sailing with just the screens in them.
