The inside rear seems to get it'self in the air a bit, did you say you were full hard on the anti-roll bars?
I remember reading that when dialling out understeer this person preferred focusing on getting the front to grip more rather than the back to grip less (ie. stiff rear ARB settings) and used the roll bars as the last resort to adjust the balance of the car.
Do you need more static camber at the front or more caster so you get more camber in turns when you need it? -1.75 is what I could find for camber.
