: after 2.5 years, I've just
: about had my fill of this project.
: I have some concerns about how safe tandem kayaks are in rough conditions so
: there is a limit to how far I'll go with this boat.

If I may suggest, finish your fill coats and varnish, throw in a couple of seats and launch that thing to see how much you enjoy paddling it with your family. I realize that you still have many unfinished experimental facets of this yak that are still uncompleted, but you are realistically close enough for a prelim launch. Go for it, try it out. This may give you a better idea of how you want to lay out the cockpits.

The skin deck will probably take you somewhere between 20 to 40 hours to complete (that's totally a guess), so why not get it right the first time? The large opening in your deck is like a blank canvas. Use your ingenuity and artistic imagination to create a cockpit configuration that works well for its intended use and think of a skin finish that will give this boat the look it deserves. You've done a marvelous job on this boat, take it out and enjoy it. Let everyone know how it goes.
SMF

PS: Have you considered MAGNETS?