Square Piano Hammer Tails

[pcpoulson at sbcglobal.net]

Good Morning: I am hanging a new set of Ronsen hammers on a square piano, 
and am puzzled as to how to correctly shape the tails and set the checking. 
The bass and tenor sections have straight tails, although the treble section 
has the modern arc on the tails. I retained some of the original hammers as 
samples, but still am trying to understand how a basically rectangular tail 
is shaped and adjusted for proper checking.
Any help would be appreciated.
Patrick C. Poulson
Registered Piano Technician
Piano Technicians Guild