[Kevan]

The only time I see too much grip is on a tight twisty Rally stage and the cars struggle to slide the rear end round hairpin bends, especially if there's something in the middle of the bend that the rear of the car gets stuck against. 

On the main club track I can never have too much grip, high grip = fast lap times.

If the car is rolling over due to the high grip I keep adding ballast between the motor and front axle until the car stops rolling over.