I've posted the same question on a few sites. I've recieved some "information" from Jack Harrison's book and the paperwork he sent out with his bows (you actually void the warranty on his bows if you use a flemish OR any type of dacron string!), and he says he's done tests (a difference of 8-10 fps according to him), but that's all so far.
A side question--anyone ever heard of B-60?