You do get that if you make a smaller guy bigger it slows him down and reduces his stamina, doncha? That the advantages which allowed them success would be reduced or neutralised? It's one of the (many) reasons why P4P is such a ridiculous concept, too. Different attributes are required in different proportions for success at different sizes.
This, plus the opponent might change his gameplan if the guy was bigger. Might box more instead of walking him down etc. Golovkin might have boxed differently if Brook was bigger and had more pop. Same concept in Mayweather - McGregor though not about size, but skill. If McGregor was a better boxer, Floyd wouldn't have walked him down like that. You would never see Floyd fight like that against anyone whose boxing he respects. If that was your only time seeing Mayweather box, you would think he's nothing special.
More likely for Crawford to outbox Spence. Crawford’s chin has been solid. On the other hand, Spence is a big 147 and Crawford is coming from 140, so I do wonder about how that might affect the match. The smaller Crawford will feel those bodyshots from Spence. Interesting matchup, hope it happens soon.
"Khan was beaten by Terence Crawford in a WBO welterweight title bout on Saturday after succumbing to a low blow in the sixth round in New York."
I hate that the ending got twisted into this. Amir was thoroughly beaten and wanted a way out without getting knocked out or getting embarrassed further. The low blow afforded him that, but they should call it what it was -- he quit, it was a TKO.
This fight was always a mystery to me. I mean yes Rigo was small but he couldn’t do anything. I was really expecting a lot more from him. Rigo is/was one of the best boxers on the planet. Gold medals, hundreds of amateur wins, crazy good footwork and crisp punches. But he couldn’t get anything done!