At the risk of prolonging this filibuster, you do not understand what neutral axis means. It's not roll center or roll axis. That's vehicle dynamics.

It's a term in engineering. As an example, imagine a one-inch bar. Support the ends and put a weight in the middle. As the bar is loaded, the upper fibers are in compression, the lower fibers are in tension. If you think about it you will understand that there must be a point where the fibers stop being in compression and start being in tension. That's the neutral axis. Tension = compression = 0 at that point.

When you start studying how material supports a load, you soon figure out that the farther the material is from the neutral axis, the more force it exerts "trying" to keep the piece in its original shape, resisting the load. At the neutral axis, the material isn't doing anything to resist the load.

Ever wonder why an I-beam is so strong for its weight? That's because most of the non-working material at the neutral axis isn't there. An I-beam puts most of the material as far as possible from the neutral axis, meaning that most of the material is working hard to resist the load. The web itself only has to be strong enough to resist crushing.

R.