The above diagram details the key dimensions for the base of the fin. This base design will allow the maximum amount of fore 'n' aft adjustment in the slot. It is also highly recommended that a very shallow groove be machined from each end of the fin to a point 1/2" beyond the default screw location. This groove allows the screws to be securely located when tightened against the fin, reducing the chance of the fin falling out should the screws become a little loose!
A PDF document containing full size dimensions for the base can be downloaded, the document is 56KB in size! Click to download PDF