And yes 18" rims are required. The ken tie rod has a small bend in it so when you turn the wheel to full lock, the inside of the rim doesn't hit the tie rod. With 18" wheels and a roll center corrected heim joint tie rod, the wheel clears the straight tie rod.
Using spherical bearings as ball joints in the control arms instead of actual ball joint, you would never need replacements (if mil spec is used) and they would be 100% adjustable. So every time you do something on your suspension, a quick measurement at the alignment shop, a shim or 2, then bingo, perfect alignment for the best suspension behavior and handling.
Basically roll center adjustment is to retain OEM geometry when lowered, widened or raced when slammed.
The car behaves the best using OEM geometry, and slamming the car without roll center adjustment actually kills the OEM geometry causing bump steer, bushing binding and so on.