How many losses should Mayweather have on his record?

[Master]

Which other "greats" started their careers at a lower weight than Mayweather and had sucess at middleweight?

Duran, Armstrong. Other guys like Gavilan and Napoles started in lower weight divisions than Mayweather started and although they weren't successful against the middleweight champ at least they had the balls to challenge themselves.

Sugar Ray Leonard must be added to the list.

If we are talking notable welters (long reigning champs like Mayweather is considered) then there are even more to add. Many of the best welters have challenged the middleweight champ throughout history.

Yet the self proclaimed ATG takes on Berto.