Just bought a 2012 Cayenne without park assist, and I'm looking into adding aftermarket rear parking sensors. I REALLY don't want to have to drill 4 holes into the bumper, so I was wondering if a compromise could be to just add 2 sensors, one on each of the circular tow hook covers already on the rear bumper?

 

Your coverage will be more limited with just two sensors.

No backup camera? That's another option..