Hi Harold,  Your posting in MMD is a bit of a challenge as I feel
there might be more parameters to evaluate.   Room size, lid position
and other ambient factors are not mentioned.

What is mentioned are the three pump pressures at normal, 1st, and 2nd
amplification, 16", 24", and 37".  Those pressures are really at the
low end of normal Ampico B operations.  Any attempt to make those
pressures lower will certainly result in several problems if the lowest
pressure, 16", is reduced.   Poor roll tracking, poor loud and soft
pedal operation, and possibly very sluggish shifting into reroll at the
end of the roll.

A freshly rebuilt Ampico B should drive the stack pressure to 45" when
the piano plays a maximum.  In a small room with the lid up, that is
just too loud for most people.  The easy solution is to keep the lid
down, and if that isn't enough, place the subdue switch (if present)
in the "Subdue" position.

Ampico B pianos play with a very wide range of dynamics.  When properly
adjusted, that range sets it apart from most other pianos.   While
Ampico "A" pianos can play almost as loud, they will play too loud in
the medium ranges if stack pressures go above 35".

Duo-Art pianos have the same dynamic range as the Ampico "B", but
roll editing (style) and other factors often fail to exploit its full
capability.   It is the Ampico B's ability to play very loud at times
while the mid ranges stay moderate, that gives it the distinct
character.

Are you sure your vacuum gauge is accurate?   Many different original
amplifier springs are found in the model "B", but they all yield
minimum pressures above 16".   I would be very cautious about making
the spring weaker.   Also, new hammers should usually have a mellowing
effect.  If your new hammers didn't sound more mellow than the old
hardened hammers, they may be too firm.

Bob Taylor
Missouri