I know you have been involved with trying to get a handle on the vibration issue. Is this from undersized gimbal motors or are they just not able to get the PID parameters set right? Maybe a combination of both?
I don't believe the motor size has anything to do with it. Adding weight should make the problem worse, not better. PID settings could have something to do with it, but all C23 use the same PID and not all buzz. Clearly the issue only effects some gimbals, this leads me to believe it is a calibration issue.