damper modification help

[Tvak@aol.com]

I replaced the dampers on a big old upright piano and now find that the new 
dampers are not doing their job very well.  The monochord strings all have a 
ringing third partial (octave+5th).  They are seated and regulated properly.  

The original damper felts were one inch in length, one solid piece.  So I 
replaced them exactly that way using Steinway damper felt.  As a solution to 
my problem it was recommended to me by another tech whose work with dampers I 
respect, that I split this one long piece into two smaller pieces on the same 
damper head by cutting a "wedge" into the middle.  He felt that the two 
resultant pieces will be less stiff, and will conform to the string and 
provide better damping qualities.  OK, sounds like a plan to me.

"Wedge" implies a triangular cut.  If this is the proper method of doing 
this, should the wide end of the triangle be on the string side, or the 
damper head side?  Or does it have to be triangular at all?  Couldn't I just 
cut a square portion from the center of the damper felt and accomplish the 
same thing?

Any advice, tips, or alternate solutions will be appreciated before I take 
razor to felt.

Thanks,

Tom S