Jim,  For a customer near Washington, D.C., I recently rebuilt an
early 1917 New York Steinway Duo-Art upright that also supplied the
accordions with regulated suction from the pedal regulator.  It was
clearly the original configuration with the player never having been
rebuilt before, including the original steamboat pump.

The arrangement also seemed to work well in this instrument, with
nicely responsive accordion movement, and perhaps with a little less
valve and pneumatic noise than I've sometimes heard in ones using
unregulated suction.  You can see the accordion pneumatic layout and
function a little bit starting at about 5:35 in this video:

  http://www.youtube.com/watch?v=5HmzVM63SCM 

Ralph Nielsen
http://www.historicpianos.com/