Technically it raises and lowers your front roll center, at the lower control arm position. No spacer for less roll/steering, larger spacer for more roll/steering. See if you can even tell a difference.
I tested this on the rb5wc. Thicker shim gives more mid/late corner steering. I didn't like the feeling. I thought the front end took to long to settle in the corner. Car became inconsistent.
On another note I ran the Cody turner setup from petit and it was very good. Better then the Japan setup imo.