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Contra-rotating aircraft propellers came into service at the end of WW II. These props offered a number of advantages including lower asymmetrical torque, higher efficiency, and smaller propeller disk (allowing shorter landing gear). There were disadvantages, too, chiefly that of increased complexity. This complexity resulted in the delay of contra-rotating propeller entering into service.

What would be the result if practical contra-rotating propellers entered into service earlier, say 1943?
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