Hi F40fan,
There are two ways both exceptable in there own right. As above lowering will/may change the camber off the rear axle but if you require a set height then there is very little adjustment built into the standard suspension to allow adjustment even for tracking, I know this as I had this problem myself and could not get the tracking in the required tolerances I required.
The way I adjusted my camber/tracking for the rear suspension was to take the measurements I had and made tapered shims to bolt between the rear arm and hub, therefor changing the setting to what I required.
Bit of a bodge is to fit washer between the arm and hub, ie if fitted to the 2 lower holes the camber will move in the direction you require and by changing the thickness of the washers will gain the required adjustment. As I said I made tappered shims for a better displacement contact area but I know of poeple that have fitted washer on high power cars and had no problem.
It's cheap and easy too
