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I have always had to use the xsaitekpanels plugin to make them work.
http://forums.x-plane.org/index.php?/files/file/14646-xsaitekpanels-linwinmac3264/
Go to this link
you can download the zip file, there is a pretty length manual along with the code.
By the way, I did see a post from Sparker, the author of xsaitekpanels, that he tested the plugin with X-Plane 11 and it was working. Here is the thread, his comment is the first post in the thread.
http://forums.x-plane.org/index.php?/forums/topic/109873-x-plane-11-working-plugins/
This site is no longer being actively maintained.