Royal was something else! he was a short time world champion who fought everyone available, including Alexis Arguello, Wilfredo Gomez and Eusebio Pedroza. And he was a hard puncher with 27 f his 35 wins coming by knockout and according to Wikipedia, he was encouraged to become a professional precisely because his trainers noted how hard he punched even as an amateur! I was reading a WBC ranking from 1981 and Royal was the number one challenger to Salvador Sanchez at one point that year! The question here is not whether he beats Sanchez or not, as the answer there is quite obvious, but could Kobayashi prove a challenge to Sanchez for a few rounds?