Support for barrel and shulker boxes was finally implemented in the plugin, new configuration sections will be created at the chests.yml to change the type of container of each chest.
Code (YAML):
container: # You can choose between CHEST, BARREL and SHULKER_BOX type: "CHEST"
+1 New feature!
This is a BETA version, please be cautious using these types of versions because it might present some bugs in the worst cases.