I have the same car, lowered with Neuspeed sport springs(same height as yours). Installed camber kit to the front and washers to the back, but it's still negative, it did gave me a little less camber after it was installed. So my tires still wear more inside and i'm actually about to buy new set of tires.

You might want to look into getting an SPC ball joint, not really sure if that would correct the problem but just do a research before you spend your money.