Hearns fought Benitez with one hand, more or less. Mayweather would obviously be fighting a two handed version. The question wasn't "would Mayweather last the distance with a one handed Hearns at LMW".
Hearns KOs him and im a huge Mayweather fan Mayweather isnt half the fighter he was at SFW. I agree with Robbi they have said all the points i would bring up so i wont bother repeating them
Hearns lands the right and stops him. Simple as that. Mayweather isn't immune to punches: Judah hit him, Castillo hit him (especially with that straight right) and DLH hit him. Hearns is faster and more lengthy than all of those guys. Mayweather gets hurt and stopped.
Floyd might go the distance if he is in a totally defensive survival mode right from the start and gets a lenient ref who lets him get away with that without stopping the fight at some point while Hearns is flurrying. Even then, it's a tough prospect. Otherwise it seems highly doubtful to me.