I noticed that the highest rating most fixed heads receive is a 4, for grouping with field tips, but most mechanicals receive a 5, for flying just like field tips. Could you elaborate on the difference between a 4 and 5 rating in your tests? For some reason, I'm a little confused what the difference between flying like and grouping with is?

I'm assuming you are simply screwing a test head on an arrow with a known field tip impact point, then firing away, but who knows.

Thanks!