I wonder what's the importance of making sure the APM/IMU is dead center the airframe.
no questions about it should be at the correct 'yaw' (ie. facing the front motor)
and being parallel to the arms and not tilted.
but at the X,Y plane must it be at the dead center of the arms crossing ?
what is actually the center ? the center of the board ?
the accelerometer is not at the board's center, which makes me doubt it's important to center...
what do you say ?