The replacement of hammers in a grand piano should not necessarily
increase the touch weight of the keys.  In fact, it is possible to
replace the hammers and reduce the touch weight.

It is possible that standard stock hammers were used and that no effort
was made to shape the hammer tails and reduce weight.  The piano action
on the Ampico player grand varies little from that of a non-player
piano.

You did not say whether any other action parts were replaced, and if
so, did the action go through a complete regulation.  Any problems
experienced with hand playing are amplified for the player mechanism.
A human can compensate for action problems, while the player mechanism
cannot.

Here is a list of things that could have changed that would cause the
problems:

1.  Increase in hammer weight

2.  Damper lift timing.  Dampers should not begin to lift until hammers
have traveled half way to the strings.

3.  Improper let off and after touch adjustments.  When slowly
depressing a key, the hammer should raise to within approximately 1/8"
of the strings, drop slightly, and slowly rise back up.

4.  Insufficient key dip.  The key should be able to play the notes
softly and the hammer go into check without hard pressure on the key.

5.  Bad action geometry!   Rarely one finds a mismatch between the
whippen and the capstan, and / or other action parts.  We have only
seen this in one Marshall & Wendell Grand.  The geometry was such that
the capstans on the keys had to slide along the bottom of the whippens,
instead of operating in a rolling motion.  This did keep the piano from
playing softly.  Correction involved redesigning the whippens and
moving the capstans.  This resulted in the softest playing Ampico we've
ever heard.

6.  If hammer shanks were replaced or the knuckles replace, it is
possible that the buckskin on the knuckles could be reversed.  Buckskin
has a definite direction to its nap or grain and must be properly
oriented in its relationship to the jack in the whippen.

7.  Relationship between the stack and the bottom of the keys may have
changed.

8.  There may be an upstop rail located in the whippens and across the
action that may require an adjustment.  This is real easy for a piano
technician to miss if he is not familiar with players.  This rail
should have been raised before action regulation and then lowered to
its proper position as the last step in regulating the grand.

Hope this helps.

Bob Lemon
Lemon's Player Piano Service
Sacramento CA