I've tried many ways to make this helicopter flight stable with a hidden tail rotor but it makes no change. The helicopter will spinning like a fidget spinner on the air. I've tried to descaled the size on Overload, nothing change and keep spinning, I'm increasing the power, also keeps spinning. But whenever I use the normal scale and exposed tail rotor, it just flying so well.

I'm calling all SP users to help me fix this tail rotor and make the helicopter flying stable and balanced. I'm suck at making helicopters with heli rotors and I know about it

Here's the unlisted build, do whatever you can to make this helicopter flies stable.