as far as weight/power, it's hard to say really. Most of the time, bombers like Hearns or killers like Duran, almost always have a harder time hurting men as they go up in weight. Roy Jones was lethal as a middleweight and although he took out a lot of lightheavies, he had to work most of the time to do it. But, it's not impossible for a smaller man to hurt a larger man, same as any other punch, if a guy catches you right, you'll go. I've seen tommy hearns stagger the iron chinned Ali in sparring, doesn't mean much because ali was 40, fat and old but it was done. Ali was also badly hurt by bob Foster in their fight. More often than not though, the elite in higher classes can take more punishment than the elite in a lower class, pfp. I still think Alexis Arguello should have been able to at least drop Aaron Pryor but he never did, Aaron was dropped by Cervantes, Kameda and Johnson, none of whom I would think had comparable power to Alexis. Sometimes it's just how you catch a guy, when you catch a guy and where.