The title is a little misleading because I have filled 3/8 to 1/2" bow rail holes from the back with glass cloth and resin. The gelcoat can says to apply to appx 20 mils, I'm more like 1/8"+ on all the holes. Is it okay to just fill a 3/8"-1/2" hole to the top with gel? Maybe 20 mils isn't that important on small areas? This would be a lot easier than trying to build it thicker with resin. Thanks in advance- Dave

no, they will pop back through. To do it proper all edges need a scarf to blend over otherwise there will adhesion and flex issues along the perimeter of the hole. You can get away with filling chips and stuff but holes need to be ground back.

Dave, thanks for your response. I'm really wondering about the gelcoat thickness in the bolt holes. Can I put the gel in these small spots without worry as to thickness? Thanks again!

Don't know if this is the right way to fill bolt holes, but this is how I have been doing it. I drill out the hole to the next closest wooden dowel size (the $6 hard oak dowels, lol), cover the dowel in glue, press it in, cut flush, sand back, fill, sand smooth then gel or prime and paint.

Opinions welcome on this.

its kinda pushing the limit but you could give it a try. Try to clean the hole out with a small rat tail file or something, you can also stick a piece of tape over it while its still wet to help level it and keep the gel in.