Geometry question

[A440A@AOL.COM]

Newton writes:
<< he hammer should be 90 degrees to the string except when it
is not.  Tipped down hammers require a longer shank which is
supposed to make a better tone.  I prefer to duplicate what
was there unless I have a very good reason not to. >>

 This is pretty topical to the bench right now,  I have a early 80's 
Bechstein M in for new hammers and shanks.  The hammers are all leaned 
distally from 90 degrees.  They hit the string off axis also, even with a lot 
of wear.  The lengths the hammers are hung vary from 131 mm to 126 mm, and 
the shanks are shortest in the middle of the scale.  All in all, an odd bunch 
of measurements. 
   I am going to hang trials at 90 degress, adding from 1 to 3 mm in hanging 
distance to keep the strike points together and just see what happens.  Any 
Bechstein experts out there think all this inconsistancy is normal?  
Regards, 
Ed