Not being a SOF builder and agreeing with the other comments, would it not be helpful to determine the number of stringers and then "line off" each station as if you were lap strake building. This would mean dividing each form equally by the number of spaces between stringers. So if the distance from keel to gunwale at the center station is say 6 ft. and you have 5 stingers then the spacing would be 12 in. (6 spaces between 5 stringers) The distance on another station from keel to gunwale is say 4 ft. divided by the 6 spaces equals 8 inches between stringers, and so on This should give you nice lines on the boat like strakes on a traditional wood boat. Or maybe I completely misunderstood your query.