Why don't you put the spring ratio equal (I use the springs equal for AWD cars), like 9/9 or 10/10, the damper bound and rebound at 7 in rear and in front, the camber put at 2.0 at front and 1.0 at rear, the stabilizers at 6 in rear and in front , I don't think the car will very different, but maybe little different, if the car continue understeering, at spring ratio put like 10/8 or 11/9, stiffer in front and softer in rear, this should cause more oversteering.