The easiest way to determine the stringing scale is to measure each
string with a micrometer, take careful notes and replicate the string
diameters which were used originally.  Many bass string makers have
computer software for piano "scaling".  Certain information such as
string lengths, termination points, bridge configuration and placement,
etc., is needed.

In the case of a barrel piano they would also need to know what notes
go where.  For custom scaling, paper patterns marking front termination
points along with bridge pin and hitch pin locations are required.

I once had the challenge of restoring a piano given to me in a "million
pieces" -- missing parts including all strings.  I could not find the
scale for this piano in the "Travis" book.  I was very happy with the
stringing scale that Arledge in Tennessee made for me.  Arledge
advertises custom piano "scaling" in the PTG journal, I would highly
recommend them: http://www.pianostrings.com/ 

Bill Maguire

One of my current projects is an Italian barrel piano which I hope to
get ready for Coney Island opening day April 5th.