With regard to Kent Zacherl's message requesting mandolin rail info,
I have built two kinds of rail, the only difference being the item
attached to the bottom end of the leather straps.  The common variety,
using metal clips, is not only hard on the hammers, but with the shape
of the clip it does not hit all three (or two) strings at once.

To me, the one that seems to work best involves gluing a fiber disc
(Player Piano Co. no. 769: 1/16" thick by 1/2" diam.) to the back
side (string side) of the leather strip.  It produces a less harsh and
consistent sound, with the disc striking all three strings uniformly.
The hammers strike only the leather of the strip (the side away from
the disc).  I think the resulting sound is more like that of a
mandolin.

Bill McKeown