Glenn Roat asked about stiffener material for pumps [260731 MMDigest].
I use Tandy Leather Hand Bag Stiffener. They sell two different weights
in big sheets.

I size it with thin hide glue and let it dry before gluing to the cloth
or leather. I weight it down to a level surface until it's thoroughly
dry. This helps it to bond well and not curl when applied. I also weigh
it down when applying it.

It's the best material I've ever found and I've used it for leather
and cloth pumps in band organs, coin pianos and pedal pianos.

Randy Hayno
Louisiana