I am working on a Hobart M. Cable player piano.  The zephyr
pouches were eaten so I replaced them with sealed leather pouches
and put in smaller bleeds.  The valve throw seemed excessive so
I reduced it to about 1/32nd-inch.  The pneumatics are tight and
the chest is tight when the tracker bar is taped off.

When I apply 10 inches of water vacuum and start uncovering the
tracker, the vacuum gradually lessens when about half of the holes are
open.  Any ideas what is going on and suggestions for improvement?

Nevin Engle