I built an OI by sizing the forms at 90% (kinkos copy). I prefer 17' boats, so I moved the forms in, staring at the ends, by 1/2", leaving the proportions original around the cockpit, ending with a 17' boat. I like it a lot (5'7", 135). It is not as stable as the original, but it is a really nice boat. I also built a Petrel and adjusted the deck downward about an inch in the cockpit area, gradually returning to the original specs (inch, 3/4,1/2...). I like the fit of that too. You can adjust any boat, just don't do anything that would dramatically alter the paddling characteristics. Picture is of a full size and my adjusted OI.