Check out the Klepper website. They have several great pictures of the frame of their boat. It is 17 feet long. Print out one of the pictures and use a ruler to measure where the seats go. A little math will translate those measurements into some full-scale numbers which will help.

You cna probably go with the distance between paddlers, and the length of their open cockpit -- both specs you can derive from measurements of the pictures on their site.

However, the location of the cockpit is going to be a bit different as the hull shape of the Walrus different lines than a Klepper, and the center of gravity is going to be in a different spot, which may be further forward, or further aft than on a Klepper. If you make the cockpit opening a bit longer on your Walrus you'll be able to shift things along the floorboards for proper balance.

The Klepper site is neat. To open it you move your cursor to the kayak frame, and watch what happens

www.Klepper.com

hope this helps

PGJ