Damon, I think I can safely assume that the hammers will be made by Schaff
Piano Co.  In my opinion, they have an excellent hammer division.  But
only _four_ hammers?  I always send the first and last hammer in _each
section_ of the action. For most grand pianos that's 8 hammers, and in
most uprights it's 6 hammers.  However, almost all upright hammers change
angle around the middle of the scale, in the tenor section, which would
necessitate sending two more hammers, or 8 in total.

Did the technician mention anything about shaping and tone-regulating
the new hammers after they've been installed in the action?  This is
imperative.  All new hammers need to be shaped due to the fact that
cutting the hammer set contorts the face (crown) slightly, giving it a
concave shape (see Pg. 315, #8 "The first filing", in "Let's Tune Up"
by John W. Travis).

Further, shaping helps insure that the strings, for every single note,
will be struck at exactly the same moment, putting them vibrating "in
cinch". Also, it is usually necessary to harden or "dope" the hammers
in the extreme treble section (the last octave or so) since they are
typically too soft and will not produce good tone.  Tone-regulating is
an art and is 100% necessary if the beauty of a new hammer set is to be
fully realized.

John Tuttle