I use holesaws with a drill press whenever possible; they are tricky with hand held drills. With a hand held I use a heavy duty 1/2" drill at 800-1000 RPM with the workpiece clamped to the workbench. I did use a 1/2" radius quarter round router bit to chamfer the inner side of the mounting holes to allow me to get in there with a tube of silicone sealeant to seal the drivers to the baffle.