Thanks for the feedback. I was trying to use the technique Nick showed in his video, see link below.

https://www.youtube.com/watch?v=cjW7Vj7e-7c&list=PLnPW0gzxQ0Njas9MxSw-N2KIRunRRTNTO&index=1

I can't tell from the video how thick the coaming lip is or how large the radius is.

Experts make it look easy, huh? :-)

The smaller the cockpit (I can't tell how large the cockpit is in Nick's video, but it looks on the small end of the spectrum) and the more 'curved' the outside shape, the thicker the rim can be and still hold the sprayskirt.
This is one argument you will find that favours smaller cockpits.
People I know who paddle rotomolded plastic boats (which have thicker cockpit rims than glass boats) usually tell me that they need to be more careful about sprayskirt fit. Some plastic boats are/were quite notorious for popping skirts, partly because of the (thick) rim design (with straight sections) and partly because the boats were flexible enough to build up air pressure inside the boat - not a problem with a stiff wood-core hull.

Trying to get the edge a bit thinner has good & bad aspects: Good=grips the skirt better Bad=harder to wrap glass around the edge.

If I follow your thinking, there would be no fiberglass on the thin outside edge of the coaming lip. Is that correct?

Not exactly - the part of the rim 'beyond' the wood is just epoxy between two layers of glass. But my cockpit rims are thinner than most wood rims.

It's better IMO to try to emulate Nick's approach than mine, with a wood rim.

No matter how you build the rim, as long as you can grab the rim and roll over the boat when the cockpit is full of water, or lift an empty boat by the rim, it's strong enough. I'd try to have a continuous glass layer (overlapping) all the way around the rim- from under the deck, around the rim and back down to the deck again.