Kenny,
I would say no more than 350lb on the front and 150lb on the rear. However, I run anti-roll bars, so if you were to remove these and run compression struts, then you would need to compensate on harder springs. However, I would try the spring rates I have quited, because given your 300Kg lower weight than my own car, you might find them surprisingly good.

As you're doing short sprints, try 3° negative camber all round and a small amount of toe-in (0'20") for stability.