fiberglass column repair
Bondo will work for small holes in fiberglass. It is polyester based, the same as fiberglass but is high in talc. All polyester products shrink forever and Bondo will eventually crack as plumguy pionted out.
To correctly fill these holes: Grind them open to a ratio of 6:1 or more based on depth of original substrate. If the skin is 1/4" thick, you will grind open the holes to 1-1/2" or more. Use vinylester resin to embed patches of 6 oz. fabric into the cavities, roll out all bubbles and let cure. Grind all below surface level, wear all safety equipment. Buy a few PreVal sprayers, gelcoat, acetone and PVA. Spray the gelcoat and cover with the PVA, let cure. Remove the PVA with alcohol and sand nearly smooth. Repeat the gelcoat/PVA until it stands proud and sand it all down. You can now buff or paint.
All of the above are epoxies and require the catylist MEKP (Meththyl Ethel Keytone Peroxide). Don't forget to add it to any polyester products and mix well.
To spray the gelcoat, mix with about 30% acetone and double up on the hardener.