Fitzsimmons was also a middleweight when he fought Dempsey. Fitzsimmons was also small LHW when he fought Gardner. Gardner had 30 KOs in 42 wins, doesn't sound bad. Besides, we are talking about boxing ability and Gardner was decent boxer who was also almost twice younger than Fitz.
Gołota gave Bowe hell, Jeffries was more durable and also liked body attacks. Not that unreasonable to see him struggling.
Bowe said Herbie Hide him him the hardest and was visibly hurt a few times by Golota. Jeffries hit harder than these guys. IMO, Bowe doesn't match up well vs punchers, a reason he avoided Lewis and never had matches with the likes to Tua, Morrison ( Bowe's manager didn't want the fight after Morrison defeated Foreman ), Ike, and others.
So what? It wasn't easy to outbox either one of them. Fitz was good fighter who used variety of tactics depending on opponent and adjusted very well during fights. He didn't try to outbox Corbett, he just wanted to land powerful punches to the body. Which is why he lured Corbett with his wild swings to the head, Jim thought that he was safe because he dodged these punches. We all know how it ended.
So being fit 219 lbs is not a proof of him carrying 220 lbs well? Come on, you just argue for arguing sake.
I base it on 4 books on Fitzsimmons and others, and over 100 years of boxing evolution . Do you think Dempsey and Gardner would be champions today? How many of Dempsey's opponents had over 15 total fights? Seventeen fight Jack Johnson totally outclassed Gardner who resigned himself to defeat early and just settled for lasting the distance.