I haven’t been able to get FCK to do anything like re skinning, to adding extra plug-ins or even recognise the specific style sheet.
Unlike TinyMCE WebYep does not control the plug-ins and look of the the editor it just references the editor. With TinyMCE it actually controls its look via the rich-text-tinymce.php file which is inside the editor folder which is inside the program folder.
As I mentioned above after a lot of messing about, I couldn’t actually get FCK to add plugins or change its skin, unlike Tiny MCE which I could so I gave up with FCK and went back to using TinyMCE.
If you do work it out, I would think a lot of people would be very pleased if you could write down the sequence and post it here.