How much vibrations you getting from the heli?
What are you using to mount the gyro?
Ball should be about 5-6mm from center of servo.
On specktrum the gain sould be around 75%.
Gyro's Delay should be set at 0.
Forget about the RATE mode setup, not needed to with this gyro.
This is what I did to get the tail to work good. I got the cloned gy401 but work the same.
0 all trims on ch4, set the gyro gain to 75% HH light should come on.
on Gyro Delay 0, Limit 100%.
Install the ball on close to center.
Loosen up the servo holder screws you.
Push the rudder left and right very slowly so you don't damage the servo when it binds up.
Adjust the limit and servo location until you can slide the tail slider 100% both way without binding.
If you follow T-Rex direction it doesn't work well with HBK2 because sock slider doesn't give you full range.
ಠ_ಠ HBK2 built with inexpensive parts! ٩๏̯͡๏)۶ Gaui425