I tried hard not to weigh in on this one but I gave up and here
goes.  Any discussion must include a description of or a "Statement
of Work".  I will focus on a pumper only for this discussion.

I prefer to break a rebuild into three areas: (1) the lower pump
assembly, to include the reserves, Tempo controller, stack cutoff
and associated hardware; (2) the pneumatic action stack; and (3)
the upper assembly to include the wind motor, transmission, spool box
and tracking system.

A customer's piano not only needs to play but it needs to look like
it was rebuilt.  On the lower assembly this would include new cloth,
hinges, flap valves, all pneumatics sealed internally and externally
with all metals wire wheel brushed and painted as necessary.  Any worn
pedal parts, bushings, pivots repaired or replaced.

For the stack, new cloth & hinge, pneumatic boards and all airways
cleaned, bleeds inspected and cleaned, new pouches sealed, valves
replaced as necessary, all screws wire wheel buffed.  I use a rock
tumbler, dry for the hundreds of tiny screws, new leather nuts on all
lifters after the lifters are wire wheel cleaned, the up stop rail
cleaned and refurbished with all exposed surfaces refinished as
original.

For the upper assembly, I would include rebuilding the wind motor,
bearings, pneumatics, polish the crank and refinish all exposed parts
to original.  I would buff the tracker bar, refinish the spool box to
original, clean and adjust the transmission.  If the roll tracker
mechanism is pneumatic, replace everything, refinish everything.

Now, for reassembly, the stack is placed into the piano without the
upper assembly, connect a suction box and operate each note and
regulate as necessary; assumes you have bench tested the stack already.
With the stack regulated and back on the bench, install the upper
assembly, add tracker bar tubing and reinstall in the piano and test.
At this point the tracking system is adjusted as necessary.

All associated rods and levers are connected including but not limited
to play-rewind and tempo controls.  Finally the pedal system is
connected testing the tempo regulator and adjusting as necessary.

The goal is to have a well regulated player play with only one pedal.
After you get it playing with two pedals, use only one, if you got it
right you can still play it.  There other components, such as sustain
pneumatics, soft bass and soft treble, that are beyond the scope of
this discussion.

To do it all as I described, should take around 250 man-hours. The
"player from hell" will take more, a Story and Clark less, replacing
all valve surfaces more, deck board repairs and stripped screws more.
Sometimes a previous rebuilder used other than hide glue and you tear
up the pneumatic bottom boards and you have to make a new set, adding
more time.  I carefully sand all pneumatic edges, I have experienced
adhesion failures when leaving the old glue.

Now, with all this said, 6 days or 60 hours, maybe, if everything goes
perfectly!  If you are only doing the stack and overlooking the valves,
and resealing, then it's a repair, not a rebuild.

My 2 cents,

Walt Gerber