XRAY - Model racing cars

What's the difference between changing track-width with shimms at the bulkheads and changing track-width with wheel hubs?

there are a few differences. 1 being the fact that the center ofthe tire is moved farther away from where the shock mounts on the arm, which will affect the leverage the shock has on the arm. Second is the fact thatthe tire is a bit farther from the shock on the arm, you dont have the rim rubbing the ball on the shock either.

If I want to make car more wide or narrow I use shims at the bulkheads. If you use thinner shims in the front, car gets more steering. If you use thinner shims in the rear, car gets even more steering and less grip.
If you use less offset in the front, car gets more steering but if you use less offset in the rear, car is more stabile and gets more grip. If is offset bigger, car is more agressive with more steering.