Another idea:

Do a search in the archives for posts by Paul Stomski. He built a triple and could not decide between cockpits or hatches, so he made very large hatches that could come off, to reveal cockpits. some of his later postings had a link to his webpage, which has lots of pictures.

Last I saw he had not yet constructed the three coamings, but as I recall, the plan was to make two lids for each position: a solid one to serve as a hatchcover, and one with a coaming, to convert the respective areas into fore, middle or aft cockpits.

Since you are constructing the boat yourself, you might consider this. You could make a dozen (or more) oversize 'hatch' covers and fit them each with a different sized coaming to suit whatever particular paddler or paddling conditions you might encounter. Round, keyhole, oval, whatever. If you are using the boat as a double, converting the extraneous center area to a cargo area, secured by a solid hatch, can be an advantage.

Hope this helps.

Paul G. Jacobson