Even with a cover you have to guard the coil and keep from bumping or grinding it on solid objects or gravel as much as possible , its only plastic. The closer you get the coil to the ground the better depth capability you have but I strive to maintain a little distance between my coil and anything hard , it takes a little work and practice but I dont like throwing my money away , I want stuff to last. I used spray on bedliner on my ace 250 coil , it worked good at keeping abrasion from the coil but being so soft or flexible it dont absorb shock from accidental impact at all. The coil on my pro is coated with clear epoxy , its hard so it takes some of the accidental impacts without transfering it to the coil , and can be put on in layers between cure times to make it as thick as you want it. If some does eventually come off I can just put more on. It dosent damage the coil and I am told it dont hurt the warranty , though I didnt check on that part myself. Its difficult to get it spread on the coil neatly so mine dont look that great , but if I damage the coil through 3 coats of epoxy then I am doing something seriously wrong. The down side is its pretty permanent once its been applied.