As the title suggests, I have a theory about Choppers advancment during the time skip. His previous limit of Rumble Balls was 1 every 6 hours, but against the Kraken he used a Rumble Ball, and then he (presumably) used another Rumble Ball to use his Kung Fu Point.
I doubt the time between those points was 6 hours, though, it might have been. And we dont know if he uses a Rumble Ball to use Kung Fu Point. Maybe he uses a different kind of ball, that allows different transormations. Maybe, but Lets all hope that his Rumble Ball Limit is much better than before