I am curious about this. I have never built a board, but these upstate NY winters do get long, and I am toying with the idea of giving it a shot. I have worked on yachts for years and toured many boat building plants and am comfortable with the process. But I don't know where to start with shaping. I am about as average size as you can get and thinking about building a light wind board. Realistically, I can see shapes: 1,2,3,7 and possibly 9 as options. As for a Roc and Con, I am really at a loss. I know in the snowboard world some manufacturers are releasing reverse rocker boards, but I am not sure how that would handle in the water. I am sure many of these shapes have been tried, and I am curious about the pro's and con's of each. I know the line drawings are crude, but for the new guy like myself, I think it's good place to start.
shapes with sharp edges can spray you in the face
more rocker helps prevent getting sprayed, and helps performance. a flat rocker is very hard on the legs because you have to force the board to plane at an angle (puts too much stress on your back leg).
rocker 1 (continuous) tends to have a smoother shape than rocker 3 (progressive), rocker 3 is more of a wakeboard rocker. Ideally you want something between 1 and 3 so it planes smoothly, rests well on both legs and has some pop. Increased rocker leads to a lot of pop, but too much makes it impossible to ride since it plows through the water like a bulldozer.
Concave 3 is what you want, it lets you channel the water in a groove through the board, concave 1 and 2 lets the water slip through. concave helps your landing because it gives an additional place for the board to flex and it keeps the board tracking well. You don't need concave though.
A normal looking kiteboard is usually best, rounded at the ends, with some rocker, a bit thicker at the middle.
When you are building a light wind board you want several things to happen
1) very small rocker (but not entirely flat). somewhere around 3 to 4 cm of rocker is what you want
2) not too much curve. This gives you less pop than an aggressively curved board, but also less resistance and better planing
3) a lot of width
4) rounded corners to prevent spray in your face
Experiment. It's possible to kite with anything you build.
Also, get your snowboard out during the winter and hit those frozen lakes.