needs a few more degrees to enable the bottom of the coilovers to clear the side of the wheel
In which case, adding more negative camber via the top mount won't solve your problem. Remember the strut body/spindle/hub/wheel are all in a fixed position! Adding negative camber just rotates the whole assembly in at the top mount. If you use spacers then you may hit the inner fender with the top of the tyre, in which case adjustable top mounts may help. If more negative camber is required you could always slot your inner wing holes as per many of the race cars
If you really need to change the strut/spindle inclination, a drastic move is to retube the struts (and with height adjustable threaded tubes at that). BTW, e12 struts add positive camber, i.e the inclination angle hub spindle to strut body is greater than the e9 (if i recall rightly it is about 2.3 degrees difference). The e12 strut is an option, the increased inclination moves the top of the wheel away from the (spring area) of the strut body, you could then use adjustable top mounts to reintroduce negative camber. Suspect it is a road car so drastic negative camber is not required. The e12 strut also gives you the option of using e12 M535i or early e24 struts with the larger diameter spindle. The e9 hub still fits, its the increased internal diameter of the bearings that takes up the larger diameter of the spindle, the outer diameter of the bearings are the same.
