"Drums of liberation" uh? :zorothink:
If the giant straw hat in chapter 906 belonged to Joyboy, we can easily assume he was a giant. If the drums of liberation are literally drums and they belonged to Joyboy, it must mean they were giant as well. Drums like this:
Now, if you turn them upside down, you get a set of drums like this:
...namely
Drum Island.