I think we're all really talking the same ranges of FOC. Easton's recommendations generally keep you pretty safe.

When I was discussing the drag connection, I think it was in relation to shooting a fast setup where you can get away with lower FOC than for a slow setup, by virtue of the fletches exerting more influence due to drag(increases as the square of velocity). But that was in a 3D context. With broadheads, the effects at the front are affected by velocity equally at the back. You can certainly get broadheads to fly at lower than recommended FOC, but performance over a given range of conditions may not be equal as a higher FOC arrow of the same build.

As far as nose-diving, this effect of FOC is hardly noticeable over the Easton recommended ranges of FOC, even out to 90-100 yards, that I've been able to tell(it may be more noticeable with straight fletch, no offset or helical though due to the lack of torque moment thru the arow shaft).