Since no one has answered it yet, here is the answer to the question
regarding the pallet valve on the soft pedal pneumatic.

It is supposed to be connected with a tee to the signal tube to the
number two accompaniment dynamic valve.  This causes the number two
accordion pneumatic to close whenever the soft pedal is on, supposedly
compensating for lost motion caused by the hammers shifting.  There
are two connections on some pianos possibly to allow connection to the
number one valve also.

Much popular music is too heavily soft pedal coded (my opinion) for the
upright players and I like to turn the soft pedal off sometimes.  This
can cause a problem as the number two might be needed at this point
although most rolls have number two on whenever the soft pedal is on
anyway.  Fortunately I can play the piano with the PowerRoll and can
remap the soft pedal to number two.  Another possible solution to the
mushy pop rolls (I never notice this effect in classical rolls) is
to connect both the number two and the number one to the pallet valve.

Spencer Chase
http://nt.mcn.org/spencer/