Regarding David McQuaide's question, I recently restored a Universal
Player Piano with the metal drilled wells and the plastic circles force
fit down over the pouch edges.  I visited with Durrell Armstrong before
doing this job and he recommended regular pouch leather circles glued
in with his number 320 glue and then sealed with a thin mix of rubber
cement and naphtha and then dusted with talc powder.  It worked very
well and my personal belief is that I would put more faith in a proven
leather product over a man-made product that may or may not degrade in
the future.

Regarding the on-going discussion about sealing pouches, my feeling is
that you need to duplicate what was there originally.  If the pouches
were thin rubberized cloth, zephyr skin or treated leather, I seal the
new leather pouches with a thin rubber cement/naphtha mix and dust with
talc powder.  If they are originally unsealed leather I go with plain
leather.  It has worked for me.

Larry Schuette
The Player Piano Man
Raymond, Nebraska