If you have been boating a long time, chances are you know people that have hit rocks hard enough to shear huge chunks of a blades (or entire blades) off aluminum props without internally damaging the lower gear case or prop shaft on an Alpha drive. They just installed a new prop and kept boating. A gear case that can shrug off the violence of a hit like that is not going to be damaged by a fraction of an ounce (or even several ounces) of prop imbalance.
The big, tapered roller bearings that support the prop shaft can easily cope with unbalanced loads. Think about how unbalanced the loads are on a car wheel (that uses the same kind of bearings). There's probably 800 lbs or more of load pushing up on the bottom of the bearing on a typical car wheel, and -800 lbs at the top, when just rolling along straight and flat. Throw in some cornering, bumps, and braking and the loads can become huge. Those bearings usually last the lifetime of the car, even if they are neglected.
Put a brand-new new aluminum prop on a balance stand some time (I made one when I repaired and modified Alpha props years ago), they are rarely perfectly balanced. They don't need to be.
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