I'm not familiar with that car, but basically the point at the intersection of the tension link and the lateral link forms a virtual lower kingpin joint.
The problem is that as the spindle rotates the virtual ball joint moves with respect to the spindle, so your castor angle and scrub radius and KPI change with steering lock (and to some extent with jounce).
It can take a long time to optimise the geometry, but it gives you more options with respect to scrub radius and KPI tradeoffs.
Cheers
Greg Locock
SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.