I am actually thinking of going to the 3M tape method. My primary reason is that I'm so OCD, having my plate off-centered drives me crazy. (If I actually saw my plate while driving my Pig, it wouldn't have lasted this long, for sure!)

 

If the tow hook plates affect your parking sensors, this plate blacket may be a better option. It still needs a couple of holes drilled, but it is underneath the bumper:
http://www.skenedesign.com/FPBracket/Choose.shtml

 

There's not really a decent flat section 'under the bumper' on the Cayenne for mounting that kind of bracket. I suppose "something" could be cobbled up. I considered that, but it looked like the bumper skin would probably have to come off in order to find suitable materials in which to drill mounting holes. Just screwed into the skin likely wouldn't hold (and is the 'hole' reason most of us are trying to do this).