Another race car trick might help. The rear of a 911 with torsion bars is tough to align. Similar concentrics used on that as on the rear of our E53's. I've had luck with pulling the concentric out, installing slightly smaller shank bolt, then prying on the control arm to move it further to gain more negative camber, then grinding the cam on the original concentric to fit it back in. On the X5, might do it in reverse- pull the concentric bolt, out in one that's maybe 2mm smaller shank size, push in the control arm to get the camber correct, then machine the original concentric to fit it back in. I bet you could get 1/2-3/4 degrees of negative out of it. I've done this on 911's for probably 20 years and have never had a problem with one.

Another option is to try H&R. They make concentric bolts for the front of our E53's, which are similar to the old VW Golf alignment concentrics. I got a pair for the front of mine and was able to get an additional 1/2 degree of negative camber out of the front of mine. Before that, I couldn't get loser than -1 on the left front, and -1.1 on the right front. Now both sides are at -.6 and the thing tracks much better, and tires aren't scalloping up like they used to.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R