Anything will vibrate when a harmonic frequency reaches a wavelength that is equal to the length between the object's fixed end and its unfixed/unsupported end. Bar snakes dampen the resonance and may be the right solution for you, solid bars, essentially do the same job, different materials and different wall thickness also work by changing the energy level required to initiate vibration. The assumption here is that all bars are the exact same length with the same bends at the same places which is rare. I spent a lot of time looking for bars for one of my builds and found that all the acceptable choices had minor, but measurable differences.
Before you purchase new bars or accessories for same try this: loosen the bar clamps and slide the bars as far right or left as you can and see if the vibration changes, it should. You can fine "tune" by moving the bars back toward center a mm at a time and see how the the vibration changes. If and when you get a "dead" side measure the distance between the center of the clamps, multiply by 2 and that should be the correct overall length. To proof this testing do the same on the other side and see if you get the same results.
The tension on your ISOs, the type and condition of your headsteady, the torque on the cradle to engine bolts, your weight and the RPM all play parts in this drama. An unbalanced engine will produce vibration similar to what is referred to a "rocking couple" or over a greater deviation from a vertical plane, a balanced engine produces vibration that doesn't deviate far from the vertical plane, but there is no such condition as perfect balance across the entire RPM range especially when you have so much weight rotating and reciprocating. It amazes me that a Norton crankshaft at 7000 RPM has more energy than a hand grenade.
The goal should be to choose a set of bars and/or accessories that keep the bars in a "comfort" zone until the ISOs step up.
Best.
