In this Xray Tech Tip video, Alexander Hagberg shows us how to adjust the roll center on an X4.
He starts by explaining how to adjust the roll center via shimming the lower arms
Here's how I remember the basic effect of adjusting roll center via the lower arms:
He then explains how to adjust roll center and camber gain via shimming the upper arms. I found the upper arm shimming advice that Alex gives to be the opposite of what I expected. This is due to Camber Gain. Alex says:
Finally, Alex talks about axle height adjustments
Add shims = takes away grip, free up the car, more corner speed
Remove shims = more traction, more grip
Remember to adjust your droop number. Example, if you add a 0.5mm shim, you need to remove 0.5mm from your droop number (4.6 would now be 4.1)