I thought that off centered trailing arm bushes were more for toe correction, but i'm told rather unreliably that they can do camber as well... I've got -2.5deg on my car on the rear - lots and lots of grip and fun on the back, but a bit of a pain with tire wear on the street. IE sell a kit for camber adjustment, but you need to weld and grind to get it in.
If you've got -2 deg on the back, personally i'd just leave it.