My biggest problem with FOC is how its tested. I can't figure out a way to test only foc and eliminate the other variables that changing foc causes. For example if I increase the point weight like some do to change foc, I'm changing not only the overall weight but the spine and in some cases the length of the arrow which changes the flight. How do you add weight to the point and retain the same spine, there aren't 50 different spines to choose from so the only way it to shorten or lengthen the shaft which changes the weight and therefore the flight anyway.
So how do you isolate the foc to see any difference or is foc just a grouping of different variables under one name?