Yes, it's very common for helis. It's because the moment of inertia in the X (along the boom) axis is quite a bit higher than the Y. The Rate PIDS always end up quite asymmetric for similar reasons.
No autotune for tradheli unfortunately. But I can usually tune them up in about 30 minutes or so. On this one, I guessed at the PIDS based on my 600 electric and had it flyable right from the start, so I'm getting better.
I suffered a crash yesterday after almost two hours of total flight time. Post crash analysis determined that the battery on the GPS vibrated loose. I took a lot of care to vibration damp the Pixhawk, but neglected the GPS puck. Once the battery was loose, it probably shorted some things inside the GPS circuit board. Whatever it did, it borked the Arducopter process in the Pixhawk, which led to loss of control. So obviously the root cause was the mechanical failure of the GPS puck. This was my fault as it was hard mounted to a frame with extreme vibrations. And it should be clear, that the Pixhawk can handle the simple loss of the GPS/Mag. But the battery bouncing around in there would have caused it to short out some things. We'll be looking at the WAY that it failed, and try to get it to perform better. We know that 3.9 seconds before the crash, the IMU logging process slowed from 50Hz to 15Hz. It could be that the battery shorted the 5V bus, taking down the 3.3V, and the MPU6k reset and defaulted to a slower speed. Trying to protect for this sort of thing starts to get a bit insane, but we try.
One thing this project has done is expose me to lots of people from other countries. Especially Australians... I'll be calling all my friends Mate pretty soon. I think chuffed is British. 
