We had used fire hose, attached in a wavy pattern on our dock. It did leave marks on the boat, even though it's a private site with no other boat traffic. The drip molded decals on my buddy's x7 were even gouged a bit over time.
I agree with an earlier comment that states the best option is to have vertical posts that will contact the rub rail. Our dock now has vertical 2x4's through bolted to the deck that work well.