Bernt Damm cited problems with a Weber Duo-Art upright in setting the
expression levels.  I have a Weber Duo-Art grand, and I have had
significant difficulties in getting the expression levels set properly.
This is not to say that I have succeeded yet.

I have rebuilt the expression box, and recovered the accordion
pneumatics, and the action and response of the accordion pneumatics
appears to be excellent and fast.  I set up the accordion pneumatics at
1/16" increments, as prescribed, on the bench using a dial indicator.
But when installed in the piano, the vacuum levels ramp up much too
rapidly, and playing the test roll reveals that each succeeding level
is too loud.

I then adjusted the accordion pneumatics in the piano to achieve (close
to) the desired response from the test roll.  This required closing up
each of the gaps on the accordion pneumatics, the ultimate result being
that I do not get the full 15/16" travel for level 15.  My minimum
vacuum level at level 0 is about 6".  Maximum vacuum level at level 15
is about 25".  It works better than ever, but I don't believe that it
is exactly correct yet.  I would also welcome comments on how to
improve the system response.

Ray Fairfield