Like several has pointed out the is no best ratio or optimum. Aerodynamically speaking, there is no such thing as too much FOC. I've been playing a lot with extreme FOC and the further forward the balance point is, the better everything gets. Folks like bow/arrow combinations that are forgiving, the further forward the FOC is, the faster the arrow will correct if disturbed, be it a poor release, twig, or small children....O.L.
Edit, I read that one paper by Don Morrison, he states arrows will drop faster with a more forward FOC, that is a myth. All else being equal a farther forward balance point will shoot flatter cause it doesn't burn off as much energy correcting itself...O.L.