I would add only one comment:  The Duo-Art system may have been pieced
together and installed in your piano, but the likelihood is that your
piano originally had a Duo-Art and that it was not a later installation
from scratch.  (I am assuming that this is an above-keyboard installation,
not a drawer installation.  Am I right?)

As for the "correct" operating vacuum (and I'm ducking behind my desk
as I write this for the arrows and bullets that will soon be flying
my direction!), do whatever sounds good to you on your piano.  If it
crashes out at 45" but sounds appropriate then set it for 45".  If you
want to set it at 30" of vacuum, it can also sound exquisite, only not
so loud.

Eli Shahar