There is no adjustment with the 15 dollar camber mod.. any more wshers and you run the risk of breaking something. To be within specs you need to get a rear camber kit that adjust a full 3 degrees. I believe it is basically shims, but it distributes the force evenly so you aren't putting stress on that bolt or suspension pieces. If you get the correct camber kits, and go somewhere that knows what they are doing they should be able to adjust it for you. Either estimate it visually. You should be able to tell if the wheels looks straight. Chances are if it looks straight to the eye then its probably within specs. IMO of course :)