The rear is only about .5" lower than stock. But I have a '95 US Spec M3, my stock rear is a lot lower than yours.
The rear fenders are pulled out pretty severely, basically the factory quarter edge angles down to 90 degrees flat towards the ground, while mine continues the outward slope of the higher part. Probably a 10-15mm difference at the bottom of the fender edge. 215/35/18 tires.