As a player restorer in the US, I too can be intimidated by player
action brands which I am not familiar.  Take my word for it, the
"Licensee" stack is a heck of a lot better than that awful "Red" Welte
double-valve stack.

I opened the stack to see what was inside.  I didn't have a clue how to
get at the valves through the glued-together stack with secondary and
primary air channels running throughout.  I also didn't know what to do
with those tiny zephyr skin pouches.  I called some of the best restorers
around the US for help with the stack, and they mostly said "I don't
work on that crap", or something to that effect.  I returned the
mechanism unrestored to the customer.

Kohler Industries, which made the Standard pneumatic action, acquired
the Welte patents seized by the US government during World War 1.  The
Licensee stack is the same as the Standard upright stacks made during
that time.  Welte "Licensee" stacks are oriented differently to fit in
a grand.  The Standard double-valve works well and is easy to restore.
This stack is, unfortunately, affected more than most others by humidity
changes.  The early double-valve stack is not as good as most Aeolian
but the later single-valve stack might be.

I use Player Piano Co's kid skin on both primary facings and the
secondary valves outside facing.  The kid skin does not stretch, and
this is important!  The bottom primary facing is often a press fit and
the secondary outside facing should not slide back and forth on the
wire stem.  The inside secondary valve facing is a "patent" type
leather, similar as used on shoes.  I usually recondition the leather.
I wipe the lacquer on and sand it flat with my valve sanding device
that chucks in the drill press and allows a quick change of sand paper
disks.  I repeat the procedure a second time.

Replacing these facings is difficult and time consuming.  I have a
"puller" for the collars and a drill press will work to reinstall them.
The biggest problem, all collars must be pulled off and reinstalled
through the non-threaded end of the wire stem.

Bill Maguire