The only time I have seen anything that was connected to two valves
on the stack it had two larger bellows that served as loss motion
compensators.  It moved all the lifters up.  It was connected to the
soft pedal pneumatic suction and prevented chatter from loss motion
during soft pedal operation.  I have seen this of several Ampico A
models, grands and uprights.  I may have pictures somewhere if I can
find them.

Don Bryant - Bryant' Antique Players
Mesquite Texas
http://www.bryantsantiques.com/

 [ A drawing of the Ampico B action, showing the wind chest
 [ spill valves and the lost motion compensation method, is at
 [ http://mmd.foxtail.com/Tech/Ampico/index.html  -- Robbie