I have just updated the Mackie Control extension and suggest all users to update to this version. It does not contain new features (beside a more official support of the 2nd controller hack), but different improvements and bug fixes, an improved manual and a lot of new FX maps.
You can find the update in the download section of the bitbucket repository:
https://bitbucket.org/Klinkenstecker..._mcu/downloads
And I want to use the opportunity to announce that I do not plan to invest a lot of time into the extension in the future. Currently I'm involved in a live playing/improvisation oriented project and therefore I'm using Usine in combination with an own Looper-Software, which I'm currently developing. So the development of the MCU extension is cut down to only important issues (like this update ;-)).