Pouch leather definitely works better on standard accordion pneumatics.
It is quieter and is less stiff allowing the accordion to work faster.
Sealing with Dow [silicone] vacuum grease solves the leakage problem
and possibly prolongs the life.  The covering is so easy to do that
I would rather repeat it in several years rather than use cloth.

To prevent the gap from changing, you can incorporate limit straps made
of cloth or flat braid.  Just glue a strip under each adjustment block,
with the accordion pulled to the correct spacing.  Glue only at the
blocks and use a small dab of flexible glue to tack it to the leather
at the mid point between sections to prevent the cloth from folding
outward and getting stuck in the adjuster screw.  I have never had an
accordion stretch after adopting this method.

Spencer Chase