As you have a narrow car I think you should try 5 degrees. I used to run 7 degrees but found 5 degrees puts a bit of life back into the steering. The maximum you can get on a stock car is approx 2.5 degrees.
I have found the wide bodied cars respond best to 6-7 degrees due to the increased scrub radius of those wide front wheels.
If you move the top ball joints forward from it's current position by 9mm it will get you close to 5 degrees. You can make the spacers yourself out of aluminium plate if you have a pillar drill. Or you can use the factory steel spacers.
Make sure your ball joint is touching the camberlock bolt while you tighten it off. I find putting a scissor jack under the hub the easiest way.