I have had the same problem on another piano, non S&S. I had some CA glue that I used to hold it in place until plate strut compression kept it in place. I would think that the whole block, stretcher assembly is alos moving in the center to accomodate the movement of the plate struts. A 1/4" length of the wedge is really no more than .002 or .004" so I would not worry about it. Newton
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