"Editor", let me preface by thanking you... since day one, i have been following your calibration advice. Been working well.
With regards to above statement, I am not sure that in Inspire's "ATTI" mode, the compass is taken out of the equation. I do agree that GPS positioning is taken out of the equation. Why do i say that? Because in ATTI mode, based on my experience, the inspire drifts laterally with the wind, but the Inspire's compass heading stays locked and does not yaw, no matter which way the wind blows. As a former RC heli collective pitch pilot, I would have felt safer, if in ATTI mode, the Inspire would drift both laterally and yawed with the wind, giving me total stick control, without Inspire's sensor/s interfering. In a collective pitch RC heli, if you had no heading lock on(i.e compass not in effect), the tail would yaw with the wind. Hence, given the Inspire's yaw stability while in ATTI mode, i highly suspect that its compass is still part of the equation(i could spin/yaw the inspire in ATTI mode, let go of the sticks and the Inspire would then lock itself into new heading and stay there - this would not happen in a collective pitch heli or any toy quadcopter without compass).
I really hope i am wrong here, because it would give me comfort to know that the Inspire's ATTI mode does not depend on the compass, but i think it still does depend on both the IMU(to maintain attitude and not flip over) and compass...