We literally are talking knives on RC planes; see the comment I originally replied to. You are moving the goal posts. A quad will tumble with the motors off, t

We literally are talking knives on RC planes; see the comment I originally replied to. You are moving the goal posts. A quad will tumble with the motors off, the whole thing is a significant lift force. It was a big problem in early controller software where throttle dead zone would turn off the props. A problem I personally experienced. Maintaining any semblance of stability requires active adjustment. And no, Ardupilot will not get anything going at high speed to within a few feet in 3d space.