Dean's FCKEditor editor width

I can’t for the life of me figure out how to change the width of the editor. I’d like it to match the content’s div width, as I’m tired of having to dork with vertical alignment of text when floating an image left or right.

I followed (and adapted) the directions I found for doing this with tinymce, but no love…

Everything on my site is updated to the latest versions. I think I just don’t know which files to edit.