The Farrand folks decided early on to develop a unique spacing in their
rolls to accommodate the absence of an effective tracking mechanism.
The wandering roll will still trigger the valves, because the tracker
bar had ports that were progressively wider from center to ends.

They are a good candidate for swapping out to a conventional 88-note
spool box assembly from another player piano.  However, from personal
experience, their tin-can valve system is extremely difficult to
restore.  I would welcome an article from someone who has successfully
found a way to restore the Cecilian valve system.

Regards,
Terry Smythe - Editor, AMICA Bulletin
Winnipeg, Manitoba, Canada