The ACS setup
Front: +5mm from strut/+17mm outward extension
Rear: -2mm from strut/+24mm outward extension
Therefore, I think for rear, that +24mm outward extension is the highest limit that you can go with. Btw, ACS did lowered the car but their springs only lowered about 1 inch without any fender rolling. However, if you are thinking of lowering beyond that reference, there is a good chance it will rub.