Hammer bore dimension

[Phillip Ford]

Since this is a political list now I'll attempt to keep this on 
topic.  Let's say that George Bush, in an attempt to make good on his claim 
that "I'm a uniter, not a divider", hires John Kerry to rebuild his 
piano (assuming he has one).  John, in a spirit of bipartisanship, decides 
to do the best job he can.  One of the things he decides to do is put on 
some new hammers.  He measures string heights at several locations and 
hammer center heights.  He had planned to take the difference in these two 
measurements and use this as the hammer bore dimension.  However, he finds 
that the difference is not constant.  Here are some sample figures of what 
he finds:

Note 21  Difference = 51 mm
Note 62  Difference = 53 mm
Note 88  Difference = 49 mm

What should John do?

1.  Use the same bore dimension on all hammers?  Why?  Which dimension 
should he use?

2.  Vary the bore from note 21 to note 88?  Why?

Phil Ford