1
...I can hear Taro chuckling at you smaking a 1 mph distinction between 88 from RRS and 87 from French but the next 4 mph not mattering...
I think the important thing to realize is that difficulty of hitting a fastball is exponential with speed and the point where the curve starts to go vertical is aroud 86 or 87 mph. So there's a huge difference between 89 and 86 but not much of a difference between 86 and 83. That's hard for some people to conceptualize.