Correct, according to the "rules" SDS, even if Medallion, are not suppose to be upgraded. However, a few months back I was traveling from ATL to RSW on like Tuesday. I had a huge layover and looked at an earlier flight on a 757 that was pretty open even in F. I could not do an SDC because I was flying on an X or V fare and the could not confirm because the same class was not available. So I SDS and there were like 4 or 5 seats in F open after UG cleared. I asked a red coat nicely at the desk and she said hold off boarding until zone 1 and if no-one SDC's, she would give me one. So I got UG...but that is not the norm.