well hole drilled in glass and no broken glass, didn't bother doing a practice hole as I've seen it done a few times.
i took the tank out side, stood it on end so i was drilling onto a flat surface, got someone to hold the garden hose and made it a nice and cool, kept the hose going for the whole cut,started off on an angle then leveled the bit out, took it very slow only 10 secs at a time then flushed the grove out to get rid of all the glass files, got some tape onto the reverse of the glass to stop the drilled bit of glass from falling.
took about 20 min all up from prep of the glass to finished including a finishing Polish
tank is 10mm think to give you an idea of time frames.
oh and a really cool tip for someone that wants to have some fun, half way threw the drill stop and look threw the glass side on, the cut looks extremely Trippe