"Some persons have very long arms, and the arrow length for them may be more than 28 inches. However, it is better for such a person to shoot a 28-inch arrow, as it will be difficult to obtain arrows that are stiff enough in spine and that will balance correctly, if an arrow is longer than the standard is used."
"Remember that drawing any arrow more than 28 inches is a detriment, not an asset. The longer the arrow, the weaker the spine, and the harder to balance the arrow correctly. The shorter the arrow, the stiffer the spine, and the easier it will be to balance. Many shafts are too weak in spine, but very few shafts are are too stiff."
"Then last, but not least, the head itself must not be too heavy in order to carry; the lighter the better, and a maximum of 150 grains is desireable."
The above quotes are from the man himself, taken from his book "Hunting the Hard Way". Mr. Hill talked about the need for proper arrow balance and the ability of the arrow to carry, but to me it seems like maintaining a stiff enough spine was his main concern, obviously due to the materials available at that time. If you ask me, he was a fairly decent shot for being so handicapped by short arrows and lightweight points.
Clint