As another Half Duo-Art owner out there I felt I should reply to John
Phillips, even though my answer may not prove very helpful and may just
muddy the waters even more.  My Aeolian Half Duo-Art has four positions
on just the one spoolbox switch:

  "Standard Full Scale Rolls Pedal (Sustain) Off",
  "Standard Full Scale Rolls Pedal On",
  "Duo-Art On Personal Control", and
  "Duo-Art On Automatic Control".

When playing Themodised rolls I can use either of the first two switch
positions, and holding the theme levers all the way across will result
in the most theme/contrast being applied, while not across at all (in
the 'Loud' position) means constant full vacuum.

In response to the actual scenario mentioned, it does state in Mr.
Reblitz' book, "Player Piano Servicing and Rebuilding", that "Duo-Art
reproducing pianos will play Themodist roll accents automatically,
(with the manual levers used for adjusting theme and accompaniment
volume levels), with the 'Duo-Art on/off' lever set at the middle
(arrow) position (pre-1925 pianos) or in the 'off' position (post-1925
pianos)."

To me it isn't clear whether the 'most theme' is with levers in
their default at rest position, or when being pushed across, as on
mine.  From the few I have encountered, the norm seems to be that theme
is only applied when the player pianist moves the levers across, to
some degree.  Hopefully one of the people who know something about
these instruments can give you an answer as to whether your setup is
just different, or if it's incorrect.

Nicholas Newble