The reason the rear has a tendency to slide out is because of the Rear camber/Rear downforce. Now to correct this problem I would merely suggest to raise the rear downforce and raise the rear Camber. But when you do this it gains slight understeer. So then I would suggest you strengthen the Stabilizers by +1 front and +2 rear. This not only will offer more grip but will help the car lose its understeer it has gained. and if the rear still slides out then you can always just deal with some understeer.
Good setup other than that.
EDIT: Another problem is that the front brakes are way too high..thus when you hit the brakes the rear end raises up. Which means you lose grip in the rear. and then when you hit the gas the car oversteers. Lower the Front Brakes to around 8 or 9. Tell me if this helps.
my vote for you