Thank you Parashooter.  You are quite correct.  I have edited my post to correct the error about stacking swivel "interchangeability".  I don't know what I was thinking.  ('measure twice and cut once' is always good advice.  Especially, with gun advice and observations).  BTW - S&S Firearms, Glendale, N.Y., has repro. Krag stacking swivels ($12) and  screws ($6).  Attached photos show stacking swivel use and also 1903 National Match Army Team with novel stacking swivel/sling arrangement.

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