[rwh]

Which is why I asked earlier if this move was "anti slice"-to me it is not.
If I apply TGM ,ie I move the ball back, I hit a fade

Just an idea, but could it be that your low point (left shoulder) position wasn't as far forward relative to the ball with your regular move, so that using the Missing Piece move has the effect of moving the ball back in the stance? I don't have the book with me, but I seem to recall V.J. discussing this.

Maybe a small adjustment in ball position is all you need.