So I am drilling my tank out for an overflow bulkhead and drilled as slow as I possibly coul, didnt push on the drill but supported its weight, and had something on the inside to keep me from blowing through. Everything seemed to be going fine but when I got to looking at it I noticed a spot in the hole and didnt know if this tank was no good now or not. I cant catch anything with my fingernail anywhere I can just see it. Any help would be greatly appreciated.