I'm not exactly sure if what has been said above is true in everybody's case.... I have been able to get on a much early flight to ATL due the fact that I would rather hang out in ATL for 5 hours then the remote airport (Islip, PHL, BOS, ROC, ONT and LAX) that I was at. I think the key is to ask for SDC to ATL, not the entire portion. I don't think you can SDC for entire portion anyway since there is a 3 hour rule....