Brook looks really small to me for MW.. sure he's chubby now.. but I don't think he has a MW frame TBH.. he started at WW.. but he's an average size WW.. I don't think he'll make it @ MW without taking some injuries and all that..
If they'd bothered enforcing their mandatory (Jacobs) in the first place then they might not have had to worry
People say they look the same size.. not to me though.. same height/weight.. but one's skinny and one's chubby..
Smith/Canelo et al would get whooped at 147.. but above they conquer.. so the same guy would ultimately succeed in both weights given 2 or 3 fights etc..