I guess I'll offer up a couple contrarian thoughts.

First, if you are making a kayak for your personal use, copyrights are not being violated. A copyright is a means for preventing another party from profiting from one's work. No sale - no profit. That said it still is a reasonable courtesy to ask the original designer.

Second, you can make any shape out of wood. It just gets harder. Look at the shapes at the stern of Rob Macks North Star. Look at Nicks wood seat. It just depends on how much effort it will take to get the shape you want.

Steve