Hey, Craig, you corrected me for something I never said and certainly
didn't mean to imply!  I'm not advocating the necessity of superhuman
perfection when rebuilding (you only need that for a Green or Red
Kryptonite Welte).

My point on measuring air infeeds in a Duo-Art was that if, say, most
notes admit air sufficient to cause a 1/2" - 1" drop in stack suction
at zero level, and one note admits enough air to drop by 2", then
whenever the bad note plays it will lower the suction for all the
others too.  It will force you to increase zero level by 1" to
compensate.  Surely it's obvious that if there's something like a stiff
action part then getting the infeeds right won't make it play!

The reason I identified this test was because I got a piano where the
previous rebuilder had managed to leave large gaps when he glued the
pneumatics on.  It was nice and tight until those notes played, and
then ... nothing!  You certainly weren't talking fractions of an inch
in suction levels with that piano.  It was cheap, though.

I quite agree about 'throttling' by over-tight valves.  I managed to
set a whole stack-full like that on a bad day, and learned my lesson
when I had to take the whole thing apart again.

Julian Dyer