If you have access to a column drill, I can then suggest this tool. I found the tool to be quite hard to use with regular electric drill because it shakes the drill quite hard. Plastic also has this tendency to melt rather than make a clean cut and that makes the job hard with every tool. With a column drill and very slow speed you should succeed quite well though.
Main Computer: Intel i5, MSI H55M-ED55, 12 Gigabytes of DDR3, 3 Terabytes of HDD, GTX295 and Benq 27"