Okay, I have seen in some RSS feeds that the Thunderbird RSS reader I use that the template and theme comes through in the post. In mine it's not. I'm using a modified version of the 1.2.2 theme in my posts, although I have upgraded to 1.5.
So what I would like to do is to insert the theme into that feed, but I don't see how to do so. And the WIKI really isn't much help.