on my engines - there is very little unbalance - due to good design work by the manufacturer.
The gallopin iron on singles CAN cause problems but mostly in some rpm range which can be isolated - most of the ones I test have this occurring about 2700-3000 rpm.
The real vibration problem we see is actually reaction to the torque applied to the shaft .
There are designs for reaction isolaters which can help -a lot - BUT ultimately -all these can do is slightly soften th blow because primary impulse is simply RPM.