Will you make a plug and a female mold or carve a core and laminate over it?
I use NACA 00XX for boards. For rudders there is something called DAG section. This was used on A Class and all of Marstrom's boats including Tornados. It was explained by Martin Fischer a few years ago on his catamaran site but it seems to be gone now. I do not have a mathmetical description and always used my Tornado rudders to copy the section and scale it up or down as needed. The section has a smaller tip radius than NACA, max. thickness is 45% aft, and there is a slight hollow in the after half of the chord. The theory is that this shape delays ventilation and the onset of stalling at higher angles of incidence. I have an aquaintence that works at one of the big design firms at Annopolis and he told me they sware everbody to secrecy when it come to their library of foil shapes. This might explain why details are so hard to come by from open sources.