I have the Base 718 Boxster and I have the same problem. I have 20" wheels and I have to back out of my driveway at an angle and enter the same way. It was worse when I had my 911 with sport suspension. If I back out carefully I just slightly scrap the under guard but nothing more than that. It is a pain thought and I am not really sure how to fix it short of redoing the entrance to my driveway.