Interesting theory, Bills.
Makes alot of sense to me. With all the different masses moving and rotating inside the motor, balancing seams to be an impossible task. One thing I noticed with all my gassers I purchased. None of them were balanced properly at the factory. The magneto wheel is normally the culprit. Not only is it made from cast aluminum but it also has the magnetos built in which are heavier than alu. Even with counterweights on the opposite side it is likely off balance. Or the front face where the prop hub mounts onto has not been machined. I had one that was so much off that the attached prop hub was 0.7mm out of whack. Without a good lathe you out of luck.