re: if your body is in bounds, can you advance the ball forward while it's out of bounds?

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No one has really given the correct answer here, so I figured I'd chime in.

First off, there are two parts to this question. When is a player in possession of the ball considered out of bounds and where is the ball spotted when said player is ruled out of bounds?

The first answer is simple. A ball in player possession is out of bounds when either the ball or any part of the ball carrier touches the ground or anything else that is out of bounds, or that is on or outside a boundary line, except another player or game official.

As for the second part, this is the answer to the question. The ball is spotted at its point of forward progress at the point when the player is ruled out of bounds. However, there is ONE EXCEPTION. If the player is airborne while going out of bounds, even if that airborneness is the stride from running, the ball is spotted at the point it crosses the sideline.

Hence you can't long jump out of bounds and gain yards.

The Bowers play was reversed because he was still in contact with the ground inbounds (not airborne and not touching out of bounds) when the ball is still moving forward. Only when his knees hits out of bounds does his forward progress stop.

Also another question brought up here is about a touchdown and the ball being outside the pylon. If the player is inside the pylon but the ball breaks the plane outside the pylon, it IS a touchdown. The endzone plane extends to infinity if the player is still inbounds. It can even get crazier than that.

Imagine a player carrying the ball in his right hand toward a pylon on the right side. He jumps over the sideline and breaks the endzone plane outside the field of play. Before he hits the ground, he kicks out his foot and touches the pylon. That's a touchdown. (And to be exact on this scenario, the ball must have crossed the plane before the player touches the pylon. If the player touches the pylon with anything other than the ball before the ball is beyond the plane, it is out of bounds).