At DeBence we have been using hemp rope or, in the case of small
bellows, several strands of hemp twine twisted together to hold the
moveable board in place.  I would be afraid nylon would be hard to
glue in place, and its characteristic of stretching might be a problem.
On the other hand, it will not deteriorate over time.

We have used all rag acid free picture matte for pump stiffeners, and
it seems to have been working.  The first pump we rebuilt that way
(with thanks to Bill Black for coaching on the job!) has run for six
years, three of those years on the carousel at Conneaut Lake Park where
it got a full summer's workout.

I hope we get lots of experienced replies to this issue, we are always
looking for a better way.

Scotty Greene, DeBence Antique Music World