Frequently, string suppressors perform best when they are actually NOT touching the string. Often, I set them up about the thickness of a business card off the string. However, thats just a starting point. What you really need to do is move them in and out until you find a sweet spot. Vibration isn't necessarily bad, because almost all bows are going to have at least a little bit... but if that vibration becomes a jump, then something has come out of whack.