Hey all, I'm Back!!! Ask tommarrow as I need sleep.
DeLiBoY, I have done 4 x's 1" holes and 1 x's 2 3/4" hole in 1/2" thick glass with a rotozip bit in my 125g. I water tested them for a month with no leakage. I'll try to post a couple links tomarrow that helped me. If not, maybe I can do them for you if you buy the bit. It's $7 a bit and I did all the above holes with 1 bit.. Drop me a pm if necessary.