I would not cut a hole for those small bits of damage. I would sand the area and just lay up one or two layers of fiberglass cloth. My drain plugs are held in with wood screws.
I wet down the area that I'm going to fiberglass with resin. Then put cloth over, and use a brush to work resin in from the top as well. A good video example is here:
https://youtu.be/9jHUI0CiYbs
I just use a brush and not a roller. I would use fiberglass cloth rather than the mat he shows. Also, you want to use epoxy resin, as polyester resin will attack the foam.
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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death
https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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