You really can't fairly rate by not taking under consideration the context of the era, including the different sizes. It shouldn't make any difference whatsoever to your ratings that the average size of the heavyweight changes. None. Anyway, I've got Dempsey at eleven, currently, Volo at 15, with the suspicion that his career would probably look better after he was out of the game a bit. His kind of boxer usually looks better when they're gone, as opposed to a lot of burn-out fast guys that tend to get underrated after burning out. Case in point, Lennox's stock increased after letting everyone put the pieces together when retiring on top and Tyson with a style that rarely ages well lingers on and let's the sport retire him, and his stock unfairly plummets afterward. Volo will likely be more like Lewis if he goes in any kind of decent shape, or even if not, really. It's just one of those careers. If his opponents are in any shape to go on and sort out the division amongst themselves and increase their own meaningfulness, it will only reflect well on him.