There is a lot of variance of opinions regarding Duo-Art valve
tolerance.  I checked out all the references I could find and ended up
using a minimum setting of .032 inch.  This setting worked for me and
the zero setting was at 4 inches WG.  I kept the pressure low because
the piano was in a small room.

A minimal setting would not make any sense if the setting was done in
a dry climate and subsequently the piano moved to a damp climate.  The
valve would then be below my minimum as the wood swells.  When I opened
the factory setting I saw ranges from .035 to .049".  The accordions
cannot be choked off in the re-opening cycle because the expression
would thrown off.

Bill Chapman
La Quinta, California - 81 degrees today, breezy, 25% relative humidity