It sounds funny that the rear would have worn like that. I'm thinking they were rotated from the front. Your rear is like the B14 so you know all the adjustment you can do to it already.
There is a company in NZ I think that make eccentric (?) bushings. Do a search in the G20 forum for camber and you should find the thread. You could try those. (PS, incase you didn't know camber plates are useless on a G20. )