So, I installed a Curt Hitch on my Cayenne a few days back. I got mine from Extreme Hitch because they are local to me.
But, my one twist was mounting the plug directly into the rear valance. This allowed me to cut a much smaller hole than is usual in the valance. It also makes hooking the wires up much easier than reaching up under the dirty valance.
To install it this way I took the adapter(the piece with the flap and mounting flange) and placed it on the valance and traced around the circumference. I then dremeled a hole in the valance and slid it through and hooked up the trailer wiring harness to it.
It then used stainless self-tapping screws to affix the mount to the rugged plastic of the valance. After I took the pics I touched up the screw heads with matte black paint.
Done. Just another option. Looking forward to maybe getting the 944 SPEC on track in August.