Wow. It turns out that double chests are a hack in Minecraft and are not really containers at all. This release implements internal shims so that double chests can be used like any other container.

Also in this release:

• "/craftmatic item mark" added to add plugin-specific NBT to an activation item.
  
• The output of "/craftmatic item show" can now be copied to the clipboard.
  
• Now always creates a config.default.yml on startup to document the plugin's configuration settings and there default values. The server admin should still maintain their settings in config.yml. config.default.yml is only for documentation and any changes made to it will soon be overwritten.