Mick posted this next door - thanks Mick - great find.
http://us.rusty.com/us/blog/tag/talking-design-with-rusty/And it is well worth a read if you want to learn a bit more about board design and whats important and not so important. Its a brillant piece that is well written in easy to understand language. Get into it

eg
Given the vagaries of wetted area size and shape it is probably best to stick with the known outline area if you want to use aspect ratio as a data point for surfboard design. However shapers have been doing a pretty damn good job for a long time without worrying about all this crap.
Rocker templates for the entry to exit, or the middle third, or half of the board are critical. The curve through the few feet of the middle is very important because it influences the numbers out towards the ends. A little change or variance in the mid-section magnifies the numbers, proportionately, as the measurement moves away from the center.