Second on Dave Gentry's Chuckanut 15'. My build and finished photos are at the link below. it has a lot of flexibility due to no frames/thwarts crossing the cockpit opening and the floor is flat, so you can sit where you like for multiple/single paddlers. I bet you could rig a removable plug or run a shorter cockpit coaming to facilitate further enclosing the cockpit.

It was cheap and easy to build- my first boat. Dave is on this forum a lot, and has a website - gentry designs.

My build (cut and paste url)
https://picasaweb.google.com/106855624119188534058/Chuckanut15?authkey=Gv1sRgCJrRxra-k8TF2AE&feat=directlink#