I hope we were joking about dropping the whole piano.  I would be
concerned about that.  Cast iron is brittle.  And you may have been
joking about using the rubber hammer but I was not.

I am very meticulous about cross valves.  I lap cross seats on glass and
fine sandpaper to make sure the cross-seat surface is totally flat.  I
also sand the wooden valve surfaces before the leather goes on to make
sure that is flat.  I install the inside metal seats with burnt shellac,
just like the factory did.  I use leather that is as dense as original
and has been tested to be fully airtight.  I seal all pouch wells and
valve wells with two coats of fresh shellac.  This is more of a problem
on other brands, but we do it on Duo-Arts as well.  (No I do not use
any plastics or polys or lacquer or varnish products.)

When I re-assemble the stack for bench testing, I pressurize it and
watch pressures inside.  I pick up the end of the stack and drop it a
couple of inches and then I do the other end.  This will seat the new
valves every time.  There will be a few that are still leaking.  I find
these with the stethoscope.  I also make use of the brass valve guides
at the top.  I find that bending the guide just a hair to one side or
the other will seat the inside valve, if performing normal activation
several times will not.  I have never had to go inside and enlarge the
already-oversized guide hole.

Every time I set up a Duo-Art grand after a move, the rubber hammer
comes out: about 3-4 firm, but not hard, licks will help 90% of the
valve seating problems.  Playing the Second Hungarian Rhapsody a couple
of times will do the rest.  In doing this, there has never been any
damage done to a stack or to the newly refinished cover, and it is a
good standard practice that puts the customer at ease.  This is because
the first rolls you play on a newly moved  Duo-Art will not sound very
good.  If you give it those few taps, the customer will not have that
sinking feeling when the piano sounds breathless on the first few rolls.

D.L. Bullock
St. Louis, MO
http:://www.thepianoworld.com