I have mine mounted 180° under the soffit as well. If it tilts down to track, the return to home is low. If it tracks high, the return to home is high. The left\right return home offset isn’t as noticable, but it is occasionally off as well.
One additional issue that has been discovered and discussed is that when an object is moving under the cam, it regularly fails to tilt down to track the object. It just stops and let’s the object fall out of the FOV even though there is still plenty of tilt travel remaining for the cam to look straight down.
It is almost as if the cam firmware has a restriction in the code to keep the the Cam from tracking down into the lower cube when in the upright position so the view isn’t obstructed. But, since the cam is rotated 180°, the cam doesn’t realize that base cube is now on top and not on the bottom but still limits the downward tilt tracking. 
It was noted here by @scdorosh: