Most likely not 12 holes. I bet you can get at least 6. Of course how thick is the glass? If your doing a bunch of 40 gallon tanks you will be fine. I would just order two right off the bat if your cutting 1/2" glass
Yea, we are going to need 2-3 saws IMO. we have to drill (4) 75 gals, and (2) 100 gals.