Sorry for the delay and quality of these pics - I'm a 1-man show over here. This cutout is flared at a few different places. If you have a bezel: It might be best to take off the bumper and lay your bezel on the backside to get an inside rim - for better fit. If you're just cutting a hole - let me know and i can re-measure for pure "requirements". Here's what i have so far (and mind you - i dont have my bezel on yet, so not sure if i need to adjust any of this):
Very top part - measured about 12.5"
The next section wen to about 14"
The very bottom seemed to be 17"
Also - here's a pic of the bezel install - not sure if you need this or not: