Oscar had fought previously at middleweight against a champ in Felix Sturm so he wasn't at that much of a disadvantage plus he weighed in at 155lbs but Hopkins only came in at 156lbs so both had a bit to spare for the 160lbs limit. Felix Trinidad was that small that he KO'd Joppy in 3 rounds for his WBA title yet Joppy did full 12 with Hopkins.