To sum this up for me, I really like the... "80% of it is BORN.... you can make the guy punch better though."
It's like speed. Sure, you can teach people to do things faster, in a way, but you either are fast or you are not. Or, you have a chin or you don't, but you can train a guy to have less of a problem freezing up when being hit or to be better at anticipating to the extent that there are situations where it's not that you can avoid a shot but you can brace yourself for it on a dime. You won't have more of a chin/build to take a punch, but you'll be less likely to get obliterated. Maybe it's not a lot less, but if it's even ten percent less, that's not insignificant. And there's a monitor, electric, like a phone app, called a reduceatometer, which shows you the exact percentage you are lowering your risk of getting KO'd. It was made in...Swed-...Switzerland. A Swiss company made it.
I should elaborate on Coetzee in case some aren't across his story. He kept fracturing his right hand so doctors performed an operation during which the bones were scraped and fused into a loose fist. This apparently took some of the meat out of the fist area and made it harder. One doctor said it could punch holes in brick walls. Coetzee, who had been a European style stand up boxer suddenly discovered people were dropping like flies from that right hand. The operation immensely improved the effect of his right hand and he did go quite right hand dependant for some time before putting everything together under Jackie McCoy for Dokes. McCoy concentrated heavily on getting his left hand complimenting his right.
The old-timers like my dad always said punchers are BORN not made. Teddy Atlas one night on Friday Night Fights said punchers are born not made. Emanual Steward one night on HBO said he could teach anyone to punch hard. It's interesting to note, that Tommy Hearns wasn't a puncher as an amatuer, but as a professional, he certainly was a puncher. Did Steward have a hand on that? I think it is a "knack" that favor some guys, and others for whatever reason not so much, but I also think it depends on different factors. I think leverage, stance, and just the willingness to commit to getting behind all your shots play a big role. On the other hand I've seen Foreman and Prince Naseem throw punches that looked like there was no way it had any power, but obviously did. An interesting topic.