After doing some testing with the new main shaft and main rotor grips for the 150X, I noticed the heli was more smooth and predictable. It's a definite improvement because you are getting increased stability and at the same time maintaining the 3D performance.
The new T-REX 150X main shaft provides an excellent fit which no end float, and the new main blade holders give a more accurate feel to the cyclic control of the model in flight.
The longer pitch arms make the T-REX 150X more precise, it feels more like a bigger heli. Thanks to the longer main shaft even using the longer pitch arms you still have a big pitch range, so the 150X is fast and more precise at the same time.