Try attaching a small weight to the backcheck or the backstop. If you can get the stack out easily you can attach the weights to the undersides of the key back of the balance rail. Use calibrated weights to help locate the weights. You can also use a drill (auger agur in the field Forstner at shop) and insert normal weights into the keys after determining their location. 55 to 45 tapering to the treble. Newton
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