ok, what about installing a thin bicycle (inner hose) between Bushwacker and fender? the rubber will take the vibration and movement- so no more scratches.
Works on my license plate since a couple of years.

They come with a rubber protective sleeve now and its the rubber that rubs the paint down to bare metal...

So the rubber is not soft enough? Called Shore...

I would use the tape, and put them on. Bushwackers look great.