Taking a look at my recurves, which are all 58" and 60" AMO Bear recurves from the 1970s and 1980's, the cat whiskers on all of them are just about 9" from where the string meets the recurve of the limb. I use cat whiskers because they are waterproof, cheap and easy to slide up and down the string until I find the spot where they do the best job. I never bothered to measure before -- just slide them up and down the string and then forget them. Interesting that they are all in about the same place.
Joe