I didn't drill this myself. This was a "reef ready" tank that had two pre-drilled 1.75" holes; I just removed the big plastic overflow that was installed in front.
The trouble with drilling myself is that the standard version of this tank has a tempered bottom. (I don't know if the reef ready version is tempered too, but who cares--the holes were already there for me.)
If I had to do this all over, I probably would have bought a custom tank from glasscages or something and had them drill it exactly the way I wanted it. The cost would not have been that much more and I could have ended up with a larger tank. Lesson learned!