ROLL CENTRE SPACING. It's one of the things we have been playing with quite a bit lately. Running TC4 with BMI chassis we first ran with .5 shims all round as we had found best on the tub TC4. This was good.
Yesterday I tried lowering the rear RC by running the rear without shims. Result - lower roll centre at rear = more grip at rear = less steering. Next I'll be removing the front ones too, to see if I can get more steering and more grip. So far it's been best with 0.5 (that's 2 notch) shims all round.
There is of course another possibility. I am presently running 2.5 rear arm mounts. I couldleave the F and R spacing as it is and go to 2 degree mounts. this should loosen the rear - and give more straight line speed. Definately worth a try.
What impresses me most is how much these small changes effect the car's characteristics.