Hi Bruce, Saw your request on MMD.  I was going to get back to you
on your question anyway.  The following is purely opinion and, for the
sake of some of MMDers, acknowledged to contain heresy.  No flaming
please!

I expect that most answers you will get will be with respect to
ensuring that the blocks and glue joints are well sealed, particularly
on the end grain, and that a perfect gasket seal to the stack is
present.

I had a lot of trouble with the blotting paper washer spacers in
that, as the hide glue dried, it shrank over the ensuing weeks causing
leakage through the joint.  I finally "solved" this by doing something
very non-original and, I expect, highly frowned upon: I sealed around
the _outside_ of the fibre ring of the outer seat with silicone
sealant.  (Yes, I know this is heresy, blasphemy and the whole nine
yards -- but when one is desperate...)

I was very careful to _not_ get any into the joint itself, as this
would make if virtually impossible for the valve to be serviced in the
future.  This was some 15-odd years ago and today I might have done
something different.  Who knows?  I'm still not totally happy with them
and another refurbishing is in the cards if I ever get to it.

Regarding possible warpage of the inner seats, I would be very careful
to confirm that this is actually the case.  If it is, I think it would
be a tedious procedure to clean it up properly.  First, it will be
essential to have everything solidly supported during the machining
process.  The hard part will be doing this while ensuring that the
inner seat is parallel to the face of the tool used, which I suggest
might be a sanding disc made up to the right diameter, _absolutely
flat,_ and mounted in a good drill press.

I'm sure a light touch would be all that is needed to flatten the
surface but that you'd have to be extremely careful.  Getting the
angle right might be simplified by removing the finish from the bottom
(actually the top in the operating position) of the valve and assuming
that the inner face is parallel to it.

I would be very wary of using any type of sealant, such as shellac,
on the inner face as there is a possibility that it may raise the grain
and exacerbate your problem.

My 2-cents worth.  And we all know what that buys today.

Jim Heyworth
Sechelt, B.C., Canada