You will find much more information on this subject and get more responses by posting in the Performance Paddock forum.

That said, I have found the rear geometry on the 124 to be really critical as far as tire wear goes. When you lower with adjustable arms, you are going to add negative camber, period. Additonally, it will throw off the toe adjustment. Incorrect toe causes more tire wear issues than does incorrect camber. Good news is that toe is indeed adjustable on this rear suspension. I think by adjusting it properly and seeing that the thrust angle is correct, you could get by with some negative camber. For handling reasons, a little negative camber on an IRS rear is a good thing. As the car sways, the negative camber allows the wheels to come up into a position that is more perpendicular to the road.

I think that you will find, after posting in Performance Paddock, that the most important issue is properly adjusting toe.

Good luck,