just drilled 3 tanks all in the sides, scared of the bottom being tempered, used a glass drill bit from BRS fitted for my 1 inch bulk heads, a large drill press (made this SO EASY) clamps cardboard, water, play-doh and poured water while i drilled. I was constant and slow, let the drill do the work, don't press too hard. I don't have experience with anything else but I have noticed with the videos and things i have watched the slower and more consistent the better. good luck. It needs to be far enough from the edge so the bulk head fits nicely, other than that its really up to you. I used a towel to catch my glass circle piece that pops out when you drill it. Other than that WEAR SAFTEY GOGGLES just to be sure if it shatters or chips your eye balls are not hurt! This hobby would be hopeless without eyes.
