Since 1975, I have done several Steinway Duo-Art players with the
moving tracker bar and not the roll shift.  It is truly amazing how
well the tracker-bar shift handles rolls without damage to the paper.
On the last restoration using this system, I have played hundreds of
rolls, and have lost only two, both of which I can blame on defect in
the paper, and not the tracking mechanism.

I am able to put my most delicate roll on the instrument, and it plays
and rewinds without problems.  This particular Steinway is on my
website.  The recording was made before a final tuning.  Just go to:
http://www.pebworths.com/APSDO 

Perhaps I have just been lucky, but IMHO, the moving tracker bar was a
better system than the moving supply spool.

Al Pebworth
Chesapeake, Va.