I say exactly what desolas said. I have no problem what so ever letting faster cars through, in heats or mains. Chances are, if you try your hardest to keep him behind you, your gonna take both cars out, just not smart, but that also means not going all the way out to the boards to let them by. If they are faster, they will find a safe place to pass. usually, I will let the faster guy go, and then try to keep up with him to see where I'm missing out around the track.