I spent about the same getting mine set up, but it made a massive difference.
Have you checked the rear bump-steer? When I set mine, I ran out of adjustment. The problem I found was that as I tuned out the bump-steer by unscrewing the upper rear heim joint, it removed the negative camber and there wasn't enough adjustment to get it back again. So Sandwich made me up a new set of spacers for the inner end of the upper wishbones, which moved them further forward in the chassis by maybe 8mm. This meant I could screw theheim joints back in again and regain the camber.
I can't recall the precise figures, but I got it to something like 0.006" per inch of wheel travel, which I was pretty happy with.
On the corner balance, we got it to within 0.5kg across the diagonals with driver and ½ tank of fuel.
Paul
PS. Apologies for mixing up my metric and Imperial units.
