Pneumatic cloth -- a sad little story

I'm working on an old Aeolian stack from a Steinway upright pianola.
It is one of the old double-valve actions with the primaries on three
separate boards, gasketted onto the secondaries and striker decks.

It had obviously been re-done some little time ago, yet seemed to
suffer from massive stack leakage when more than a few notes were on.
I assumed valves were not seating, but they seemed okay.  I then took
off one of the striker pneumatics (which came off suspiciously easy)
and it, too, looked okay.  I peeled off the new-looking cloth and was
amazed to find it porous when looked at against a bright light.
I don't know when it was last rebuilt, but I would have guessed less
than 30 years ago.

Now here comes the sad part.  The rebuilder had done a conscientious
job, but had only recovered some of the striker pneumatics.  Why, I just
don't know.  He had stuck them back using thin, inferior glue and thin,
smooth gaskets, with the result that the joint between them and the
deck-board leaked.  In addition, nearly _every_ one of the new pneumatics
were now perished, whilst the old ones from about 1910 were perfect.
This clearly says something about some old types of cloth and _some_
new ones.  As I took the new cloth off I could see pencil construction
lines which he had used to cut the cloth the right shape _before_
gluing on.  It must have taken ages, and to what purpose?

It seemed so sad to me that a well-meaning, hard-working but misguided
restorer had taken ages to replace something that probably did not need
to be replaced, and turned something that did not work well into
something that did not work at all.  I hope I do better.

Regards,

Paul Morris
Exeter, Devon, England