For me the 400 stock gyro is not good, I had adjusted the gain just before wagging, everything as expected,when I tried to make a loop the 400 start to spin and should not making this.

I saw some 3D 400 videos in youtube and it holds the tail steady, dont know if they upgraded the gyro to perform this, at least from my side is imposible so far.

About the Revo mixing, be carefull, revo mixing was use only on nongyro systems, so if you use revo mixing with a gyro system it will give a false rudder input to the gyro and you will get an uncontrolled spinning heli.