Wiggs is attempting to define a bell curve, which is mighty mathematical of him. Curse all of you for trying to bring the black man down. You don't want him to start counting or learn to read. You have cotton to be picked.
I'm behind you Wiggs, though I suspect you may need to slightly widen to around 5'7-5''11, that way you have 5'9 as your top, which seems like a good spot.
Of course, there will be nonzero quantities of the heights not in this range. That is the nature of a bell curve and not particularly pointworthy.