just stiffen the shock oils and springs.
just recommending it as it would be a lot less time than trying to design your own. if you wanted to go a step further though, you could cut part of the body to raise up like an airbrake when you slam on the brakes. or pull a pin on a parachute. these will help to slow the car down abrubtly, but you still need friction brakes to come to a complete stop.