This is what the designer says:

Dimensional changes
Linear changes in a photo copier are generally a bad idea, since the different qualities are not linear. If you fx enlarge the plans by 200% (a stupid idea of course) you end up with a kayak that is 1.4 times faster but needs 8 times more effort to keep at that speed and will be 32 times harder to maneuver (see the table below). It is easy to lose control over the performance – and often better to design a new kayak from scratch.

He also says making the boat longer by I think he said 15% can be done, might want to read up on the design page for that boat.

Bill H.

Originally I was just going to stretch the the boat and raise the deck. then i wondered about expanding the whole thing I have read up on his design page (many times) and thought perhaps Bjorn had made his point just a tad strong .Considering I am only looking at a 3% increase in size .But very hesitant to go off half cocked on something so time consuming and emotionally draining if i got it wrong . i thought someone here might have done it before . i really appreciate all opinions so far
teddy