Look, Rene had a shocking chin. He was also past his best but Palomino was old, out of the game for years and Arredondo had been a titlist a few years before. A quality win all things considered. Palomino remains an underrated fighter who lives in the shadow, very unfairly IMO, of Pipino Cuevas. Here is a brilliant and very recent interview with Carlos, very revealing and he seems a real character, highly recommended http://www.cyberboxingzone.com/blog/?p=14576
Carlos did a lot of weight lifting during his comeback, while in his prime he only did basic exercises (heavy bag, speed bag, pushups, etc) and he claimed it radically improved his power and he seemed to suggest he wished he'd tried weight lifting in his prime. For what its worth, Monzon never recorded a first round knockout.
Thing is if he had at his best I doubt he'd have had the stamina he showed to finish fights late (against Muniz for example)