What makes you think that Slavin had a shakey chin? For sure he was knocked out a few times but all these knockouts come late in his career when he had descended into achoholism.
Shaky is perhaps a bit too bad, I meant because of his offensive fighting style, he was always wide open for counters for example, and he didn“t have an iron chin or so, Shavers on the other side was really a bit shaky...
I've never seen Slavin fight, so it's hard for me to judge. Slavin comes from the bareknuckle-gloved boxing transition period, so under modern rules i would have to favor Shavers. But of course Slavin should be given a good chance due to Shavers' lack of durability.