Originally Posted by YoDog

Shim at the arms to get the desired track width but you can use wheel shims to test and fine tune. In the front, use the offset blocks and add up to 1.5mm if needed. In the rear, use the offset blocks for the back mount and the standard block for the forward mount. You can add up to 1mm here as well.
When at all possible, shim the arms and use the wheel spacers only for a quick adjustment at a race event. IMO