BlenderPilot is correct about the high-altitude t/r problems, if the high-altitude tail rotor hasn't been installed. The tail rotor on the straight L was just about adequate. Put the same rotor on an L1, with more power, and it's getting flaky. Add a C30 engine, in an L3, and it's less than adequate. Make it an L3 Increased Horsepower, or an L4, and it's dangerous. Keep on adding horsepower without increasing the tail rotor or the arm, and you'll eventually run out of tail rotor authority. The high-altitude tail rotor should be required on L3s as well as L4s, and I think it's criminal of Bell to ignore the problem.