I do not think cross should be thought of as a major tuning tool. Cross is about timing of weight transfer more than anything, and it is a coarse adjustment. Timing is effected by weight, vertical center of gravity, speed, turn radius, and track grip. Think of those factors as components of G forces. More cross will resist full transfer longer, and rebound transfer sooner. This transfer is mainly off the left rear and your adjustment is the dynamic distribution of transferred weight between the two RS tires. As the components of the G forces combine to create higher G's, you will need to raise cross to preload the suspension to resist transfer more, otherwise it will transfer to a greater degree, sooner, and take longer to rebound. If cross is too low, you will be loose just after entry and remain loose through the apex and into the exit because there is not enough resistence at the RF to keep the car from transferring too much weight from LS to RS too fast. If you have too much cross, the car will not transfer enough weight off the LR soon enough or long enough and the car will push from just after entry until, through the apex, and on exit.
Spring weights also effect amount of transfer and speed of rebound, as do shocks.
I try to keep my cross as low as necessary and work to get my handling with springs, radius rod lengths, camber, caster and brake bias. Cross does bind up the car and it will slow you down.
Good rule of thumb. Provided you don't have something way out of whack, entry problems are fixed with front end adjustments and exit problems are fixed with rear end adjustments.
