I have the Parts Rack mount as well. It's two blocks of really soft plasticy rubber that slide perfectly over your front air intake cross section thing and then wrap around in the back. You have to drill into the mount itself to get the screws right where you want them to hold the plate to the mount, but you do not have to drill into or damage your car. When you want to take it off (like when you travel into a no-plate state), you just reach behind it, spread the fingers apart, and pull it off. Easy peasy. I have seen no marring or damaging of my paint so far.
I do recommend that you frame out your plate though. Just a rectangle of steel or Aluminum behind it should work. Otherwise, your flimsy license plate has to hold together these two heavy plastic blocks. I don't have mine reinforced and it's bent up a bit. It looks like I run into cars parallel parking all the time, but it's just getting this way from me handling it all the time.