Greetings,  I too have been in the position of attempting to partially
restore a Duo-Art that really should have been rebuilt completely.
If one is expecting the performance that the Duo-Art is capable of you
are in for a long struggle and any results you do obtain may be short
lived.

If everything is rebuilt correctly with the best materials and
attention is given to every detail, you stand a very good chance of
having an excellent instrument when done.  You may also have to find
original factory errors or instances of sloppy workmanship and correct
them.  This is quite common and these problems were probably only fixed
for the few customers who were aware of problems and insisted on their
repair.

The operation of the of the Duo-Art is dependant on many variables.
It is possible in many cases to make compensations for problems that
have not been repaired, such as sticky or leaking knife valves or weak
springs but there will almost always be some problem that persists when
a particular coding and note combination comes along.

It is very possible for a piano to be "more musical" although playing
weakly before repairs are done and then have it worse after partial
repairs.  You can then spend many hours trying to make it acceptable
when the best solution is a complete restoration.  It is also quite
likely that the owner has become accustomed to the way the piano
performed and may be satisfied with nothing better.

Another common problem is that a previous restoration was made to
work acceptably by unconventional means.  Once the piano is set up
conventionally, it may be much worse.  For this reason, it is a good
idea when attempting partial repairs to make measurements that will
help in getting things back the way they were.

When recovering accordion pneumatics, it is a good idea to measure the
existing settings before recovering.  Even if the covering is almost
gone, it should be possible to lay the boards out on the basis of the
remaining covering and get a pretty good guess of the settings.  Then
when you put it back together you can make it sound closer to the way
it did before.

Best regards,
Spencer Chase
Laytonville, CA 95454
http://www.spencerserolls.com/