The 'rigger mounts that I have are available at Sportco. I forget who makes them but they are a universal mount. The 'rigger base bolts on to a 90 degree piece of metal then that piece slides in to another piece that is bolted on to the side of the boat with six stainless screws. The side of the boat will have to break before the 'rigger mount will. Very strong.

Maybe Winterun can chime in here with the brand name of the 'rigger mount.
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Carl C.