I suggest you look at some of the books on kayak building. Some include drawings and measurements you cna use to recreate your own full-size plans.

One book in particular, David Hazen's book on strip building canoes includes full size patterns for several canoes and two kayaks. He explains how you can easily adapt these for making at least one more design.

Larger people may find his patterns for a double to be of interest, although his singles hold 500 pounds.

Hazen's book seems particularly valuable. In addition to the patterns, his information on assembly will be of interest. Unlike many strip builders who start at the sheer (or gunwale) line with their first strips and then add strips towards the middle, fitting each one, Hazen suggests starting in the center of the hull, along the keel line, and using full width strips. Once the central area is filled, creating a roughly 'football' shaped oval, he trims off the excess, making only one edge one each side that needs to be mated with a curved, fitted strip. The illustrations in his book show this process better than I can describe it.

Hope this helps.

Paul G. Jacobson