Experienced Auto Repair
It looks like you are looking for a rear camber adjustment. There is actually not one built in from the factory. It is possible to buy aftermatket eccentric bushings for the rear trailing arms arms but that is the only way to adjust the rear suspension.
Bavarian Autosport sells this kit. Just search under your vehicle/rear suspension.
Bavarian Autosport Adjustable Camber Kit - Rear
$269.95
I'm sorry I took so long to get back to you.
I'm not sure what kind of kit would be weld on. I'm not really sure what would be welded other than tabs to adjust the trailing arms.
I have seen a few of the kits offered on bavarian autosport installed and they should be able to adjust the camber in more than 1 degree.
BMW Master technician
BMW S.T.E.P. graduate, 10 years BMW dealership experience