I think that I understand what you are getting at..........
You might wish to pack out the 8mm using a suitably sized spacer or plain washers. However, remember that the angle of the damper will change depending on the undulations in the road surface across the axle as well as relative to each rear wheel.
There is a reason why flexible bushes are used at the damper mounting points - it is to allow a degree of flexibility as the suspension rises and falls.
