I am in the process of rebuilding my 88-note (6 holes to the inch)
Melville Clark Apollo Concert Grand pushup player of circa 1904 and
I have a question regarding rebuilding the very small pneumatics that
operate the primary valves in the stack.  All 88 of these pneumatics
are supple and seemingly airtight, which I find somewhat surprising
after about 107 years or so.

My question is, should I recover these pneumatics with new pouch
leather and risk damaging the probably very fragile wooden air tubes,
or simply treat the 100+ year old pouch leather with something to
improve its air-tightness and flexibility?

Opinions on the pros and cons of either approach would be greatly
appreciated.  If the opinion is to treat the old leather, what would
be the treatment of choice?

Cheers,
Alan Turner