There is a undocumented feature called "sports guard". Once enabled, it will automatically record extra on the end of sporting events

so how does it work? is it automatic? does it let you select how far over it will go?

By the way, what you're talking about is not "negative padding ability". What you're talking about is also, of course, standard on Tivo.

What tanstaafl was talking about was being able to start late and end early. Not start early and end late. The later is standard on both units, I gather. So does Replay have the first one?