I'm certainly not speaking from any experience with that vehicle, but just looking at the pics, I can't imagine that you'd have to do anything more than pop out the tail light assembly. It just doesn't make any sense that you'd have to do anything with the bumper. But sorry, without actually inspecting the car in person, it's almost impossible to tell for sure.
As for off-axis, this is true. You just rarely see a cop directly in front of you. He's almost always off to the side of the road, or on an overpass. This has lead to some speculation that angling heads off-axis may be beneficial. However, to this point, all testing indicates otherwise. In order to get the maximum amount of support from BOTH heads on each shot -- from any direction -- it is best to have the heads perfectly aligned straight ahead. Having both heads capable of contributing to the counteroffensive is key to success. And keeping the heads spread as widely as possible positions them for maximum off-axis effectiveness. That's why mounting in the green would be your absolute last choice.

