Hi all, it's been a while since I've been on so Im not sure if anyone has said this already but, I think it's fairly obvious that Kuma ate the "Size" fruit. Which is why his height appears to change here and there. He can change his size at will and when he touches anything he can directly change it's size.
When he was standing in front of Perona, he wasn't as as tall as when he was standing next to Gekko. Also, Perona didn't dissapear to another dimension, she just got shrank to a really small size. Quite an interesting fruit….. I wonder what else Oda is going to make him do with this fruit