Mike .. I made inquiries direct to FCS and they were somewhat helpful,
you choice may be the TOW IN G10 fins, (if small enough) or a similar shape to the center.
The surf companies understand the force difference on windsurfing, but I don't think have a definate fin that will work. The current issue of Surfing mag has a free handout on FCS as do most "real" surf shops.under specialty fins the AB TOW IN /G10 OR AB-2 CLOSE to our fins, the TOW iN SHOULD BE FOILED ON BOTH SIDES.