I don't think you have to worry about the intentional flywheel imbalance, after all, some guys take the flywheel right off to run an electronic ignition system.

My flywheel has a cast-in key, so I balanced it on the short section of straight hole. I just made up a tight fitting hardwood dowel with pointed ends held between 2 wooden uprights with drill indentations. If you try this, make sure the flywheel runs true, no wobbles.

Allan