I built nicks guillemot s&G. I made a flush hatch and used the channelling aka George McQuades Journal: guillemot website; designs;guillemot ... down to S&G.

I tried weather strips, but the stuff I used seemed too thick. My next experiment is to paint some sort of releasing agent (olive oil) and smear some silicone aquaseal type stuff around and replace the hatch till it sets.

However, the bottom line is that the hatch looks good but leaks a little. Not enough to have to actually do something about it, but it leaks. If I really wanted it dry I can always duck tape seal the seams.

My cunning plan next time is to make a mini cockpit hatch (lip + rim just like your cockpit) and get a neoprene sprayskirt (like a shower cap) covering. It would look a bit ugly, but my bet is that it would be pretty simple to make and pretty waterproof. This is from my experience of splashing around the place and comparing and contrasting the amount of water inside my cockpit compared to my aft hatch and making allowances for water brought on board by tootsies.

If you really wanted to go "offshore" you could make a hard ply cover to cap your hatch "cockpit" and reinforce the shower cap. But most of the time I am betting it wouldn't be necessary.

Just a thought, I haven't actually made a hatch like this yet. Good Luck

Cheers Pete