If you follow up on Rehd's suggestion and look at the 17 foot version of Putz's walrus you'll find my translated coordinate spesc for that model at:
http://www.geocities.com/eureka/business/7882/walrus17.htm

I believe Rehd was able to cut all the building forms from a half sheet of plywood using these numbers. If you make these using Putz's description in the book you'll need about 1 1/2 sheets of plywood.

Mike Hanks has a boat which is closer to the original plans (drawn by a guy named Skeene). Skeene's specs are in the back of Putz's book, or you can ask Mike for the changes he made.

Once you have the coordinates you can graph the shape of the building forms and then modify them by adding or subtracting to the height or width. Once you have the basic shapes on paper any changes are fairly intuitive.

PGJ