Did you make sure to install the plugin packages when you downgraded? That could account for the Cube plugin missing. Also, you'll need to reconfigure Compiz how you want it since the newer Compiz stores it settings in a different folder from the older version. (The newer version, if configured to use the GConf backend, stores its settings in ~/.gconf/compiz-1/ (~ being /home/<user name>) whereas the older version stores them in ~/.gconf/compiz.) You might be able to rename the folder and transfer your settings that way (though you'll need to configure Compiz to use the gconf backend first, the default setup is to use flat-file storage... You'll probably still need to manually enable and disable the plugins but any changes you made should be recognized).
Linux Mint user since 2010, fluffy dragon forever!
Registered Linux User #473695