Terry, My understanding of the reasoning for the shape of the "bottom" (horizontal) shape of the flange is that it forms more of a "three-pointed" surface contact, providing more stability that a truly flat contact area. Your add-on looks crucial, (and elegant) and the picture makes me wonder if the system wouldn't benefit from a papering of the surface of the main rail where the "bottom" of the butt flange makes contact It looks as if there is perhaps too much room there, and .010 or so of shim might give a more solid base at time of string/hammer contact. Know what I mean? Guy
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