Roger,

I've measured the distance most commonly used from the tip of the solenoid
plunger to the mounting bracket stud hole and it's real close to 3 inches.
I can set the bracket to be less, or I can set things up to cover much
more distance.

As far as the difference in keydip from one piano to the next, the
solenoid plunger is spring loaded.  At rest the spring is compressed.
The amount of compression is determined by the amount of preloading.  Out
of over 50 installations, I've never had a problem with the solenoid
travel.  With too much preloading the piano plays with very little upper
end dynamics.  With very little preloading the piano plays poorly on the
lower end of dynamics.  A sixteenth of an inch can be made up for in the
amount of preloading adjustment.  The figures of x amount of solenoid
travel is somewhat difficult to understand when you have a plunger that
is flexable about it's starting point.  The people at PianoDisc know what
their competition is, and they have installed a good number of units in
Steinways.  The Burgett family is rich with technical knowhow, (pianos,
general engineering, marketing, etc.) and has your concerns covered.  I
suggest you consider calling a high volume installer that has done some
uprights.  The pianos that pass through here are mostly grands.

--- Larry Fisher RPT, Portland Metro's Authority on PianoDisc Systems
        For more information call (360) 256-2999 in Vancouver, Wa.
                      or email larryf@pacifier.com