Irrespective of whether the tail rotor or the fin is doing the work the, tail is proving a countering force to react the torque from the main rotor. As a result, some sideslip is required to counter this lateral force. Similarly, the lateral forces for most single propeller engine airplanes do not completely balance out due to the propeller’s “P” factor. This factor is really obvious in aircraft with very high power engines. The T-28 is a good example with its 1550 hp R-1820 Wright Cyclone engine. Significant right rudder was required to keep the aircraft in trim during high power settings.