As stated, the beastX, 3GX, Ikon and all other 3 axis gyros have the tail gyro built in. 3 axis is X Y Z axis, or flip, roll, and yaw. Your Yaw is the rudder. So all that is needed is the one gyro.
As Kev stated, I have my 3GX just stupid stable right now, and yes, it's on an HK clone. All of my issues were in the head, not the gyro. I may get a DFC head kit and call it done with some Align 3G flybarless blades.
I have the AR7200BX as well on the nitro, and that thing is planted at factory stock settings. But, dollar for dollar (quid for quid lol), you can't beat teh 3GX if you take the time to set it up correctly. You just have to remember one thing, the 3GX HATES sitting on the ground running. Mine on the ground looks like it's having a seizure, but once in the air, it's almost hands off. If you have a slow spool up, and put it in the air while it's spooling up, it's as solid as a rock. Then, just hit throttle hold about 4" above the ground and let it drop to land. I'm havign great luck with this 3GX. Hoping to get some videos shot tonight on the new series.