Will all those testing pouch sealants please give us an honest idea
of how much stiffer the various compounds really make pouches?  And
whether they become stiffer at low room temperatures?

In my experience many compounds leave pouches too stiff for true
pianissimo playing, especially at low room temperatures.  The
suction level necessary to shift a valve fast and securely enough
between seats must be significantly less than that required for the
pneumatic to play its note pianissimo without missing.

A good indicator of really supple pouches is that with the tracker
tube open they fall back into their wells under their own weight.

Patrick Handscombe
Wivenhoe, Essex, UK