I think fighting the larger fighters prepared him to come back down to 147 and be much stronger especially considering both him and Marg weighed in at 160 tonight.
I wouldn't go that far to discredit Margarito. It was the same old Tony. Cotto and his speed couldn't beat Margarito and Shane and his speed fought Cotto pretty evenly. What won Shane the fight was committing to his punches and holding at the proper times. Margarito was closing the gap as the first few rounds went by but Shane didn't let him get the proper distance that he needed to work. Brilliant game plan, great performance, awesome stoppage.