.../...affect the camber. Is it going to be more positive Or maybe more negative?
The spec for our SL cars is -1 degree of camber on the rear wheels, i.e. slightly out at the top of the tire. See official factory photo attached.
Changing the rubber mount in the trunk will most likely raise the diff on your car, which will affect rear wheel angle.
The rubber rings under your rear springs and the position of the plates there is the method for adjusting the rear wheel camber. Well explained in the workshop manual (BBB) and the Book of Tables.