If I was Golovkin's advisor and Golden Boy/Canelo were asking for a catch weight 158 would be the lowest he should go. Golovkin doesn't look like a skeleton at his weigh in and I think he can sacrifice 2 pounds with no ill effect. But I'm sure GBP/Canelo will ask for 155 or 156.
Did you watch it on you szhitty computer? I was there watching live in the arena and no way Cotto won more than 2-3 rounds. I gave him 3 and that was generous.