: One of the nice points of making the boat--the hole can be any size
: shape I want.

Music to me ears -- I like the way you think! More boat builders ought to be using their noggins' that way. The chief advantages to going to all the trouble of rolling your own are tailoring to fit, keeping it light, and keeping it cheap. At least, that's how I see it.

I think the way Uncle Nick shows in his book is as fast and good as anything. Talking about the "Strip-Built Sea Kayak" and a classic Guillemot coaming shape. I like the way the sporty-short ocean cockpit look the best, but I must have more open access than that, and find the egg-shaped 28" x 17" Guillemot opening perfect. Any larger is too large. I made permanent templates for it and its recess, and use 'em on all my boats, thus my spray skirt fits all.