Down-Bearing for Old Board

[Erwinpiano]

 Terry
   Sorry I forgot to address that point. The answer is yes as to measuring
the string gap at the string rest/aliquot  How large a piano is it and how
old?  I think I'd like to know that before saying anything hard and fast but
if the wood looks sound and you have new bearing values I'd push it pretty
hard And always keep the dmp chsrs on.! I know what does that mean?
        To answer that fully will require finding John H's. articles but to
cut to the chase the method I and many of my colleagues use is called a
pre-stressed method of setting bearing and is easily adapted to fit your
situation as well.  This method requires  that the board be at some
reasonable R.H.(which it is ) then installing the plate and securing at the
block,nosebolts and a few places at the rim.  At that point pull a string
thru agraffes over the bridge and see what you have in the way of a gap
between string and rest .  Lets just assume at this point your bridge is a
perfect original bridge and the height is good (which in your case is
possible since your bearing is mystically so good).  Good meaning the too
tall bridge will provide adequate bearing.
       The info gained from the next step will lead you to know if you will
lower or raise the plate shim or unshim string rest or install new bridges
to get what you want .  Cut 4 thin/small maple wedges and starting at the
central strut wedge one between the top of the bridge and the bottom of
plate strut while pounding downward on the bd. near the strut . Repeat at
each strut location then return to first and repeat cycle of pounding to
ensure even preassure on the board.
      As your pounding ( Pounding is not violent just firm and yes you do
develop a feel for this and each boards resistance is different and will
pre-compress  to varying degrees)  Once the bd. is compressed retake string
thru agraffe. readings and over bridge. The gap I want to see is roughly
2.5mm in the top treble 2.25next section  down nd 2ish in the middle to
bottom. Please these are not hard and fast and there. are variations we all
use depending on the sit. and are intended as a good starting point and one
I feel is safe for your siuation.    Usually the amount the board sinks is
fairly predictable.  I.E. 3   m.m. at the central strut 2 or so at next ten
/treb. and 1ish at the top. and 1 or 2 on the bottom. Do not over pound the
bottom it needs to flex as it's near the rim glue joint
   Hope this helps and if I left anything crucial out ( like a lot o stuff)
Buzz me another post.This should get you started
   Dale Erwin
P.S.Wish all new/young? techs. showed your persistence!