Video or it didn't happen!!!! (yeah, most of mine is borring too -- it's stil a milestone!)
The default mix should be fine if you've got stable flight otherwise -- the mix shouldn't add throttle on a yaw, but the gyro control loops should.
I've got pretty flat piroettes on mine (not centered mind you, but it's a tricopter).
I'd run the P and I gain up a bit on the pitch axis -- if the stability can take it. The pitch gyro should hold a 0 change as it spins on the yaw gyro, and it should know it needs to react as the tail starts to rotate down. If the gains are too low, of course, it won't react fast or strong enough to appear like it's got it under control for you (why have a control board if it won't do the work for you
).
Also, double check the level of the board with the frame. If your board is tilted forward/back/left/right (in relation to the props) the gyro corrections will couple on yaw. If there's a left/right tilt, you may very well be commanding the tail to droop slightly as you pivot.