I recently installed the BMR LCAs and relocation brackets as well. At the time I was stock height but last weekend I installed a set of lowering springs. At stock height I was using the middle holes on the brackets. I haven't re-adjusted the LCAs yet, but as far I know, the LCAs should be close to level, or point slightly downward in the rear. I haven't noticed any issues. Do you also have an adjustable panhard bar? I have heard that if the axle is a little off center one way or the other, it'll feel loose and cause some problems.
1995 Mustang GT, White: BBK CAI, Magnaflow O/R X, Magnaflow Magnapack catback, Hurst short throw & Black FR500s.
2013 Mustang GT Premium, Sterling Gray: JLT oil separator, JLT CAI, Pypes O/R X, Roush axle back, Lund Tune, Eibach sport lines, BMR LCAs with relocation brackets, BMR adjustable panhard bar, Steeda wing, Boss 302 rear diffuser, Stillen splitter, Billet upper grille, Roush high flow lower grille delete, sitting on 17x7 & 18x10.5 Dark Stars