
Mirror mount may be less intrusive/destructive,
bumper mount is a waste of time: high swr (bad) low signal (bad). You dont want anything metal (like the vehicle) level with the antenna if you can avoid it, pref to get it as high as possible.
If you want maximum range, get as long an antenna as you dare. I once ran a 7 footer on a transit van

You can put a spring between the mount and the antenna if needed, also a quick release if you can be bothered/want to be able to remove easily.
If you go for a small antenna, see if the guy has one of the wilson flex, or a firestik (some love em, some hate em, but they work),
have fun at pickering guys, & don't forget to pick the hams brains about it, hams LOVE cbers

