Using commercial hatch systems on wooden kayaks can be a pain so I recently produced some plans for stitch & glue hatch recesses. There are four sizes: Round 15 for Kajak-Sport round 15 covers and 6" Beckson deck plates, Round 20 for KS round 20 covers and 8" Becksons, KS round 24 covers and KS 42/30 ovals. I'm offering digital copies of the plans FREE to home builders. I hope someone finds them useful.

http://watercraft.clearstreamwood.com/shop/plans-plywood-hatch-recesses/

(NICK: Please delete the post if you feel it is too commercial.)