I've never drilled a tank before but think our 125should be drilled vs overflow box. I was wondering if anyone has drilled a tank with water in it.. maybe 30% reduction and a dam keepiong the end drilled with no pressure or water.
It's hard enough setting everything up with the tank on its side, let alone with water in it. I wouldn't recommend it. Most importantly, trying to keep the dam of coolant for the bit would be too difficult, and it does make quite a mess.