Thought I'd better share this as i've never seen anything come close in performance.
This is an FPV 250 in hover! On the left chart -- Less than 0.2g is good, 0.8 to 1.2 is excellent, but an average score of 0.01 is just nuts! I've seen numbers as low as this once before but the VDEP was dampened in a way that ship attitude variability (the right chart) suffered greatly (the VDEP was too isolated from the frame to be able to control it). Usually, with dampers, one trades lower vibration for ship control. Once the PIDs are tuned, the control numbers will improve even more.
The entire damper system weighs less than 12 grams. So little vibration is added lifting the dampers.
The design was purely a fluke. I was trying to solve a different problem and just wanted a slick and easy way to activate and deactivate a damper system.
This is how the damper is built. The damper is a 450000039-0 Vibration Damping Ball 50 gram found at Hobby King. The damper housing is 1-ply Carbon Skin 1/8" Balsa Core Sandwich Panel. The housing can be bonded with about anything. But bond the assembly to the motor mast with something good (e.g., 3M 2216). Getting adhesive (from squeeze out) on the exterior of the ball when assembling the housing is OK and actually good as it helps keep the ball inside the routed-to-fit housing when inserting the axle. The axle is a 0.155" (4 mm) extruded carbon tube. These dampers are good up to a VDEP weighing 200 - 600 grams or one damper per 50 -150 grams of VDEP. The FPV 250 had four dampers (2 on each axle).