After mounting the APM in a mounting pad from hobbyking I was able to get vibrations in the Z and the X axis to within +/- 5 and +/- 3 respectively (I applied small pieces of the pad on each corner of APM on the top and bottom and the APM sits between between the the two plates of the quad with a small amount of compression)
But for some reason the Y axis vibration is still much higher than the X axis vibration. I would have thought them to be symmetrical! See the attached picture below of the Acc X/Y/Z values in a smooth hover flight in stabilized mode. The AccX values in Blue are much smaller than the AccY values in Green. What can be done to reduce the Y axis vibration? How do I diagnose it?
PS: I'm running a stock 3DR quad with 850kv motors and ArduCopter 3.0rc3 in the X configuration.