Yes, it is very important to regulate lost motion between the stack and
piano action in a reproducing piano, as it is in any automatic piano.

This is described on page 101 of my book, "Player Piano Servicing and
Rebuilding," in the section on Aeolian player pianos.  The procedure
is the same as in Duo-Art uprights:

- Regulate the piano action.

- Restore the stack.

- Remove the spoolbox and other parts attached to the shelf.

- Install the shelf on the stack.

- Install the stack in the piano and regulate the lost motion between
the stack and piano action.  (Lost motion can't be regulated with the
spoolbox and other parts in the way.)

- Remove the stack from the piano.

- Reinstall the spoolbox and all other parts on the shelf.

- Reassemble the shelf to the stack.

- Install the tubing. More details may be found in my book.

- Reinstall in the piano.

This and certain other regulating procedures might seem lengthy, but
once you understand the procedure it doesn't take that much time
compared to the big picture of restoring an entire reproducing piano.
Precise regulation after a careful restoration can mean the difference
between a mediocre reproducing piano and a good one.

Art Reblitz
Colorado Springs, Colorado
http://www.reblitzrestorations.com/