My recomendations.
Drill out the hole and remove all debris and damaged material. then fill with a good quality filler and epoxy. I had a hole in the head of my tiger rudder head and filled it with West system. Hard as a rock and very stable. when using the resin let it fil the hole then lightly tap the rudder with a rubber malet to allow any trapped air to escape. Make sure to tape the work area off first as the epoxy is hard to get off once set. Fill the hole completely but allow a slight upward bubble to form on top. The resin epoxy will settle as it goes off. the bubble can then be sanded smooth and your good to go. Btw gel coat will not readily stick to most epoxy's so keep the epoxy as the finish coat. Hope this helps.