Yeah, the need to fight weekly definitely had a lot to do with the style back then. As for the gambling circuits, my trainer once told me that the bookmakers didn't like surprise knockouts that could mess up their numbers, so rules and style changed. Maybe that has something to do with clinch being dominant, you certainly could get taken out with an elbow or knee in the clinch, but maybe less so. I do love watching old Petchboonchu fights though, it's amazing watching him clinch.

That's fair about kard cheuk being like the 4oz gloves, I've seen some fights with them, but like you said hands never scored as high, whereas One scores things equal these days iirc.