Thanks for posting the spring rate options.
The AST c/o's should be the option for anyone looking for serious performance.
I am curious why the spring rates were advised to be so high? It was my understanding that most of the body roll and rough ride issues that the xi has comes mostly for poorly matched dampers to the springs. For example, the e9x M3 still has fairly low spring rates compared to what Harold recommended (190/550). It would be great if Harold could provide some knowledge to help us all out.