Drilling an extra hole

[spit.fire]

Originally Posted by reefwars

not necessarily , they drill the holes before tempering the glass .

are the edges polished pat?

I've never seen a factory drilled tank that was drilled on the back let alone tempered on the back

But that being said there are always exceptions

I'd say 80% chance it wouldn't be tempered

That being said your statement is correct in lots of cases, like by rr 72 bowfront

Factory drilled bottom with tempered bottom which I find to be real common on bowfronts