Markus,
When I did a forum and internet search, what I found suggested that 5 to 6 degrees was about right. When I adjusted mine, I aimed for 6. I've not really driven it since the adjustments to know if it worked, but it should have!
As I recall, there was space for one washer in the lower wishbone mounts, so only about 1mm or adjustment... Not enough to make much of a difference, but since I had everything in pieces anyway, I figured I might as well use all the space available...
Ben