Rescaling GH1 tenor section

[Matt]

Hi all:

I have a client who is unhappy with the sound of the low tenor on his 
Yamaha GH1 (circa late 70s) and has requested rescaling of that piano.  I 
did suggest the usual voicing, fine tuning, etc. and he said that he has 
already had stuff done by other techs.  He has done some research of his 
own on the Internet and has decided that he is is interested in the 
rescaling.

I have not done any rescaling personally but I understand that most or all 
of the string parameters are entered into a computer program which then 
spits out recommendations for changing string diameters here and there and 
changing some plain trichords at the tenor to wound bichords.

Then the physical work involves maybe drilling hitch pin holes, modifying 
the bridge, etc.  I read in the archive that Yamaha used to offer a kit for 
these pianos but it was recommended by list contributors to do a custom 
scale for each piano for various reasons.

So, my questions:

1) What is the best software to use to do the rescale?  Or, does anyone out 
there accept parameters and run them through their own software as a service?

2) When all is said and done, is it possible that the difference in 
harmonicity may not even be audible?

Thanks,

-Matt