i use a 1/8" acrylic template myself and always start and keep the bit completely level with the glass and never rock the bit, i always get a perfect hole with minimal chip out on the bottom side, better then the factory holes
and at least for me the cordless drill gives better speed/pressure control then a drill press. you don't use the same speed for drilling as you 'break' through the bottom. i drilled all four of those holes with the tank sitting just like that in the dining room floor using plumbers putty for a dam to hold the water and a towel on the bottom side to catch the water when you drill through and to keep the plug from hitting the other glass. took about 30 min to drill all of them, had to wait an hour for the Batt to charge first
the HammerHead will pull in from the two 1.5" BHs at the top and return through the two at the bottom.
kc