A new version of acdctl has been released which incorporates changes kindly sent in by Michael Hanselmann. The tool now directly supports one more display in the apple product line. Additionally it can now take in the vendor/product id on the command line to make it easier to test against unsupported displays.
If you are able to make it work, please send in your display information so I can add it to the set of supported displays. Part of the changes made by Michael is a restructuring of how the displays are stored internally so that new ones can be added very easily.