Filling the hole. First I used a dental pick and a Dremel tool to remove the core for a good 1/2" beyond the drain hole. Then I enlarged the hole in preparation for inserting a 1" ID (1-1/8" OD) fiberglass tube. Then final sanding and cleaning, and I put a good coat of neat epoxy all around the hole. After that (and will the tube prepped), I slowly built up the hole with thickened epoxy (colloidial silica). I had to do it in layers so it would not get to hot as it kicked (but all in the span of a few hours so it was still plenty green for a chemical bond).

Filling the hole. First I used a dental pick and a Dremel tool to remove the core for a good 1/2" beyond the drain hole. Then I enlarged the hole in preparation for inserting a 1" ID (1-1/8" OD) fiberglass tube. Then final sanding and cleaning, and I put a good coat of neat epoxy all around the hole. After that (and will the tube prepped), I slowly built up the hole with thickened epoxy (colloidial silica). I had to do it in layers so it would not get to hot as it kicked (but all in the span of a few hours so it was still plenty green for a chemical bond).