I ran the 18" with H&R 8mm's and lowered on Eibach Sportlines and thought it looked much better. I chose 8mm but you do need longer bolts for them as well as 10mm. When I went lower, with 18x8-45et wheels(225/40-18 tires), it rubbed and I sold the spacers. So, you may consider 6mm. Will not need longer bolts, won't rub if you choose to slam it, or if there's a wheel change in the future. You could do a trial viewing using washers/spacers between the wheel and hub of one corner. Would need to measure their thickness first and then stack the spacers at three points(no need to do all five bolts). Then you can set it down to see which you prefer...plus, you will see if the oem bolts work at 6mm.