Robbie,  You added an addendum to the last post which said:

 [ West Coast player tech Clare Spencer would drill a small hole into
 [ the treble and bass windways of the newly rebuilt action stack.
 [ He said when enough leakage developed then he would cover the extra
 [ holes with pneumatic cloth.

It has been my experience that as the piano is played, and the valves
seat, the stack becomes tighter, with less leakage, and will not develop
more leakage.  I'm certain that I will be corrected it this is wrong.

Al Pebworth
Chesapeake, Virginia
http://www.pebworths.com/ 

 [ I helped Clare fit the newly restored Duo-Art player action into
 [ the restored Steinway grand.  He made a quick check of the expression
 [ regulator using a test roll, and then he listened to a familiar roll
 [ for a few seconds and exclaimed, "Oh, I forgot to drill the bleed
 [ holes."  He said, being freshly rebuilt, the action had no leakage,
 [ but in a few years it would leak enough that the bleed holes could
 [ be covered.  Maybe he had replaced the troublesome "cross valves"
 [ with a different design.
 [
 [ The Ampico B has dedicated "Wind-Chest Spill Units" which admit air
 [ to the action stack at low intensities, and also permanent No. 52
 [ "static" bleeds that continuously admit air.  -- Editor (Robbie)