And Hagler had a 75 inch reach.. Hearns had a 78 inch reach,so that puts into perspective Hagler as this small guy. He was not tall, but his reach was that of a man 6ft 1 or so. Hearns reach was more than a man his height.
Weight jumping is watered down if your just looking at ABC titles. Basically you are only really stating you are 1 of the best 4-5 boxers in that weight. Hagler was built perfect for middleweight, he had lots of big fights there and cemented himself as the best in the division. I give more credit to Hagler for cleaning what division out for a number of years than say someone like Cotto who is a three weight ABC titlist who hasn't cleaned one division out.
Because he was prime at Middle-weight. No point in moving up in weight when foold like Leonard and Duran would move up to him. BTW HAGLER WON THE LEONARD FIGHT!!!
Ultimately, it wouldn't matter how weak the post-Spinks era would be since a career defining matchup(and a record breaking payday) with Spinks would be the only reason to make the move in the first place... Hagler would most likely make this move after the Hearns fight since he had nothing left to prove at MW and Spinks was still at 175 around that time so Oct-Nov-Dec of '85 would make the most since.
I think Hagler would have done well against most guys at 175 except Spinks. Spinks was such a big guy at 6-2 1/2, although amazing to think is that Spinks had a reach of 77 inches if my memory is correct and Hagler 75 as a southpaw might have made for an even fight if they boxed... Hard to say. But the Spinks Jinx might have been a little too hard for Marvin.