Have the "manual" version installed on my C6.  It gets scraped often on parking bumpers and concrete curbing meant to stop cars when bumpers aren't used.  Every once in a while, I have been 'surprised' by a bumper... and recently bent the attaching bars.  I will include a picture of the results.  However, if you don't drive your Vette that often, and you are careful, you'll probably be OK.

Note: In the picture, I hit the 'high' parking bumper pretty hard, and the forks are no longer perpendicular to the holder.  I am sure it can be adequately straightened.

Dave, I have used the motorized retractable licence plate holder for years on my C6. It worked great, even after I repaired it from its initial contacts. It was crunched so many times, by bad judgement, that it had to be replaced. The new one received the same treatment and has now been replaced by the same static model that Paul is using. They are typically not really in danger if you pay close attention to your approach and normally don't get compromised by steep driveways and ramps. The main thing is, they look so much better than the original stick-on-the-bumper version.