Well, this will open up some discussion I'm sure but here are two
things that have been done when space is too tight to fit a suction box
in the foot of a piano with the original reservoirs in place.

In some rare cases there may be enough room to mount the suction motor
in the upper section of the piano.  Use a piano hinge to hang the motor
in the cabinet.  The hinge makes it very easy to swing the motor out of
the cabinet to facilitate working on other items.  Hang the motor
upside down.

You could cut a hole in the corner of the soundboard and run the
electrical and vacuum connections through.  Then, either mount the
motor on the back of the piano or leave enough slack in the connections
to set it to the side.  This is the setup of my piano.  The motor will
not fit flush to the back so the piano will not be able to go all the
way against the wall.  Depending on the piano it's about a 2-inch
difference.

I have always thought it would be awesome to have a mechanical system
that would manipulate the original pumps while the pedals were out.
How neat would it be to see a player piano pump itself!  Just a thought
for you mechanical geniuses in the crowd!

Sam Harris
Greenville, North Carolina