only recourse is eccentric trailing arm bushings to dial in a bit more positive camber.
Then there is the issue of installing them properly to get the desired result. Perhaps someone will post who has done so successfully. All suspensions when dropped increase negative camber because suspension travel is a natural arc as viewed from the front or rear of the car. Most with lowered BMW's simply live with the increased negative camber which is more pronounced in the rear which has more negative camber to begin with. This is more problematic in staggered wheel/tire combo's as increased wear on the inside rear tires is pretty common and one can't therefore rotate a staggered wheel combo front to back to prolong tire life.
HTH,
George