Any node of vibration can be dampened by adding weight in a particular place that will null the vibration. Translation, adding weight attached to the handle bar at either the middle of the bar (between clamp and bar end), or at the bar end, can reduce vibration. The exact position and amount of weight is usually a guessing game, but it can be done. Aircraft mechanics and engineers fix hydraulic lines that like to break, by doing exactly this. Sometimes just adding a U clamp and moving it around to experiment, will do the trick. Another way is to add an extra brace across the center clamp, that supports the bars left and right about half way out. I added slightly heavier bar ends to dampen vibration. Hard to test, since there is a specific RPM that will excite the harmonics. I have nice after market mirrors, but they vibrated. They shouldn't have done that. I took them off, and added rubber washers and o-rings all over the place. Problem fixed. There's lots of tricks, just have to find one that works.