Originally Posted by Absolutely!
It's impossible to say. Some fighters would, some wouldn't. It would depend on their frame, their body's ability to retain speed and mobility, whether or not they'd feel comfortable at the higher weight and so on. Marciano reportedly felt sluggish at 200lbs, but felt at his peak at 185. I don't know if he'd be able, or even willing, to pack on twenty or thirty pounds of muscle. Dempsey on the other hand I feel would have filled out nicely.
But honestly, muscle mass is overrated as an attribute at heavyweight. I'd much rather a fighter trains their ass off to be the best they can be, and come into the ring a little on the light side, than pack on useless muscle mass that does nothing but slow them down, make them stiff, affect their stamina or whatever, just to fulfill some arbitrary size quota.
Look at Adamek. Who would you say was the better fighter, the sharp, fast combination punching machine at cruiserweight or the sluggish and sloppy featherfist at heavy? What has that added ten or fifteen pounds (accounting for weight cutting at CW) really done for Adamek as a fighter?
Now look at Haye. Enters the ring against Chisora at 210lbs (his in-ring weight at cruiser) and does the business on his larger but far sloppier foe. Look at Huck. Another 210lber who pounds the crap out of Povetkin because he isn't an immobile tub of meat, and hasn't sacrificed his attributes at the altar of mass.
One of the troubles with the modern heavyweight division is that normal sized heavyweights, perhaps out of a misguided belief that it allows them to compete with the naturally larger men, are packing too much weight. For some it's too much muscle, for others too much fat. Either way, they're not in peak condition. Haye showed that a smaller fighter who's fast, athletic and willing to put the work in at the gym can triumph over a heavier, but ultimately less talented, and less well conditioned fighter in Chisora. Chambers showed that a far talented smaller fighter could quite handily beat a much larger foe in Dimitrenko.
Anyway, I'm digressing slightly. My point is that a smaller fighter shouldn't feel pressured into adding muscle weight unless he feels it will be beneficial to him in some way. If it improves them as a fighter then I'm all for it, but the impact on performance should always be the main thing, not the end result on the scales.
No, why should that follow? Byrd was an extremely skilled and tricky fighter who specialised in fighting larger, stronger fighters and clowning them to decisions. A fighter like Young might have emulated his success, but it doesn't follow that a come forward brawler like Dempsey or Marciano would.