Unfortunately its not automatic - You select in the setup screen how long to over record sporting events.

Sorry for the confusion about negative pad. I doubt ReplayTV can do that.

I hardly ever use padding on records - it creates too many recording conflicts. I observed a very interesting behavior of ReplayTV in regards to padding. Playback starts from the scheduled start, not the padded start. I can see the logic behind this since the show was scheduled to start at that time and the pad is just in case. Does Tivo behave this way also?