need advise for drilling acryllic tank

I just bought a hanger for my led light and the hanger was meant for an open top aquarium. My tank is an acryllic with an acryllic top that is part of the tank. All I would need to do to modify the hanger is to drill out a 1/2"X6" slit on each side on top of the tank so that the braces can just slide on into the tank.. My question is... Has any one drilled in an acryllic tank with the fish still in it and any suggestion on how I should go about making these slits?



Any help is greatly appreciated!!:thumbup: