His chin did seem to increase when older. He was an absolute tank when old. Absorbed a ton of punishment, never dropped, barely even seemed hurt. Whatever the reason for it (rolling with punches better, all the weight training he did when old, extra mass, etc), old Foreman was more durable than young Foreman, and people love to give the old chin to the young guy in fantasy matchups.
Foreman was only dropped three times in his first career. One when he was dead tired, and suffering from exhaustion and heat stroke, that resembled a slip which it was initially called by the referee. And another time, when he came off a year and a half exile, noticeably rusty, against the 2nd hardest puncher (besides himself) of the era. Let's not act like he was Amir Khan in his first career. Frazier's left hooks literally bounced off Foreman's head with zero effect.
I agree Foreman's chin wasn't better in his 2nd career, he just wasn't as reckless and paced himself better. And also used a new defense in his 2nd career with the cross arm defence. Let's look at Foreman's knockdowns in his first career...... Lyle vs Foreman = Foreman had no defense in this fight, and basically fought a reckless street fight vs one of the biggest Heavyweight punchers of 70s. Again nothing to do with Foreman's chin being worse, he just fought a sloppy fight and got dragged into a war trading punches. Ali vs Foreman = Didn't pace himself, and wore himself out more than anything which lead to the KO. Again Foreman could of actually got up, but was exhausted and knew he was beaten. Young vs Foreman = As you said fighting in a heatwave, and the knockdown in the last round, was more of a slip due to fatigue and not his chin letting him down.
Prime Versions of Ali, Holmes an Tyson would beat Lewis. Holyfield an Bowe would’ve had a good shot of doing it as well
No one but The Greatest Muhammad Ali !!!!! beats a prime 100% fit & focused Lennox Lewis. But Lennox had one glaring fault he underestimated the opponents he didn't consider dangerous , & paid the price against Mc Call & Rahman. There was no doubt in the rematches was there??. He could have retired undefeated because all the opponents who everyone claimed would beat him Ruddock, Golota, Tyson, Bowe etc he demolished with the exception of Riddick Bowe who blatantly ducked him. He beat Vitali while barely 80 % fit & as for Wlad he took to the hills going Awol till Lennox retired.
No it isn't. A weak chinned boxer isn't suddenly going to have improved punch resistance from gaining weight. Otherwise David Price would have an Oliver McCall level chin by gaining more weight and every weak chinned boxer would simply gain more weight to deal with that weakness. You have no idea what you're talking about.
Young Foreman, Prime or Manila Ali, FOTC Frazier, Pre or Post-Prison Tire Iron Jones, Sonny Liston (very torn on including him, his power and jab are big threats, and his footwork could make things awkward for Lennox), Prime Tyson, Prime Louis, Marciano of the 1st Walcott fight (again torn).
Tyson 15 years younger than the one he fought. Usyk if he can beat Fury would probably be able to beat Lewis as well. Since a past prime battle worn Holyfield nearly beat him , there's no reason not to amuse a 91 version couldn't take him
Boxers fight in a certain weight class, gaining weight makes them exceed weight limit. Only HWs can afford to do it. Also, extra weight can make one slower and hinder his endurance. Plus, it's also about what type of extra weight one puts on (fat or muscle) and where it's distributed. Incresing traps and neck muscles is obviously better than putting on belly fat. Now, it's not that the extra mass makes one chin better, but bigger and stronger neck and traps muscles help your head withstand a punch better. Also, to the same extent overall weight of an individual helps him stand his ground better when he's hit.
Once again you're not making any sense. Boxers move up in weight and continue to be effective all the time. Many featherweights become champs in 2 or more divisions going up to welter. Some welters move up to jr middle and middle. Several super middles can move up to light heavyweight. If a boxer has a weak chin in a lower division he can simply move up in weight to become more durable to take hits better and this isn't even remotely true. A heavyweight boxer who has a weak chin weighing 210 lbs would have an iron chin at 250 lbs according to your logic. Fury and Ruiz add fat and somehow are very durable. Their endurance wasn't hindered at all either. Foreman also added plenty of fat, it wasn't just muscle lol. You're making this up as you go without citing any medical research or something from a fitness/boxing coach.