Since you have examples, you could obtain “real numbers” on the unbalance weights needed, by spinning those flywheels on a balance machine.

Electric motor repair shops usually have balance measuring machines for large rotors.

Hunter computerized tire and wheel balance machines could calculate a result if an adapter can adjust to flywheel center hole.

You correctly are trying to “get the correct balance.”

By knowing the numerical imbalance you could drill slightly smaller balance holes in the flywheel, then “dial in” a nearly exact balance by enlarging the holes.

There has to be matching “bob weight correction” at the other end of the engine.

When balancing large electric motor rotors it is very common that the two shaft ends need different weight corrections for smooth high speed rpms.