greaser,
Plasti-dip is too rubbery. I would advise using spray on truck bedliner. No effect on performance and hard as a rock.
Although, I have had several detectors over the years, and I have never worn through a coil cover. When you look at the price of a can of plasti-dip or bedliner, you are better off just using the factory coil cover, AND IF you wear through it, but another one. THEY ARE CHEAP!
Mike
Just remember if you can't take it off the coil it voids the warranty if coil needs to be sent in for trouble ...