Yeh Jon, noticed that comment about the roll center, interesting.
On mine, taking account of the physical limitation imposed by a front mounted rack, there is now as much Ackermann as is possible. With that plus 3mm toe out the car now turns in beautifully, its really big fun to drive Too nice in fact, to get better drive out of corners the rear end is being softened a bit. To be really quick I figure its got to be a bit of a pushing pig, by imposing more load on the front, which I now know is working well, so the rear wheels can use more of their grip for forward traction.