The factory upper a-arms are not adjustble, just the mounting bolt location is. I have -3 degrees of caster as my car is set-up with offset bushings and trying for the most caster.
I am running the factory 4 piston disc set-up & do not want to get rid of that, may just have to ream out the upper mount.
I will check those SPC arms out and I am really curious about the taller bolts, that could really help alleviate some of my caster issue.