The 16 is pretty easy. You use only the existing holes. The castings were designed to fit Euro boats, so you likely have to enlarge the holes in the casting to match your hole spacing.
The cast gudgeon more evenly distributes loads to the transome and wear on rudder pins is reduced. We advise stainless pins rather than aluminum. Unless in surf conditions where the boat can back down over the rudders.
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Hobie Cat USA