Go the other way. All they need to do is make the front car have a crazy ammount of drag. These are random numbers but lets say the car pushing has a 95% drag reduction. The fix is make that drag reduction consistant, meaning for not just that car behind physically pushing, but also for the car alone 50 feet back. This in theory would result in a closing rate like we have never seen in Nascar but, would also mean 1 car could slingshot around a tandem. He couldn't stay there, but he could blow by them.