As Robbie suggested, if the hammers were replaced with even slightly
heavier ones, due to the 5:1 distance ratio between the hammer stroke
and keystroke, this can result in a much heavier "feel" at the key
end.  And then there is the matter of improper action geometry, and
the extended key lengths, which add inertial mass to each key-lever,
resulting in a "clunkier" feel.

There are various approaches to remedying this, but if I were to
try to do so on a Duo-Art, I'd find a certified practitioner of the
"Stanwood Touch weight Metrology" system, and hire them to straighten
it out.  David Stanwood's system offers vast improvements to the
"touch" of even some of the most renowned makes (making them "better
than factory") and according to him (we've spoken) can at least make
Duo-Arts play like "normal", high-end grand pianos.

Gordon Lee Stelter
Athens, Georgia