Hi Dave,  Almost all of the Welte-Mignon regulator action parts under
the piano are mounted to a board, 1.5" by 42", that mounts to the
bottom frame of the grand piano.  The valve unit is attached to this
board with two metal brackets that are hinged at one end so it can be
dropped down for adjusting the valves.  This valve box is held up in
place with two more metal brackets.

I have a unit available but it is for a Chickering grand, not a Kimball,
and it is not in very good condition but is complete.

Pete Knobloch
Tempe, Arizona