Conclusion on Arms

As I said before there are 8 different combinations. But there are also an infinite number of degrees to which each can be done. Here is a compilation of how each one effects running.

1. Timing - Leading with the arms speeds stride rate, causes the foot to land farther underneath the body and leave the ground faster.

Timing ahead of legs = fast stride rate
Timing with legs = neutral stride rate
Timing behind legs = slow stride rate

2. Arm length - A greater difference in arm length causes a greater bend in the torso which adds power and extends the stride length.

Arms longer moving backward = longer stride length
Arms same both directions = neutral stride length
Arms longer moving forward = shorter stride length

3. Arm angle - A greater inward angle in the arm swing towards the body's center line has a twisting impact on the torso when the timing leads the leg cycle, but it has no impact when it is in a neutral timing or lagging behind the leg cycle.

Arms swinging inward = no impact unless the armswing leads the leg cycle. If arms lead leg cycle, it adds power(force) but impeeds speed via range of motion. Great for up-hills or pulling a weighted sled.
Arms swinging straight = does not add power, but does not impeed speed either. Legs move freely. Great for down hill running, flat traeadmill running (no wind resistance), and running with a back-wind.

I believe if these three elements can be understood for what they do independently of one another, then the best combinations can be used for various running conditions. For example, to increase stride rate and stride length and transferring power through the legs from the torso, (1) lead with the arms (2) while lengthening the arm length on the back swing and (3) swinging the arms halfway between parallel to running direction and across the body. Stride rate comes from 1, stride length comes from 2, and the power to sustain that form at higher speeds comes from 3.