Rss feed: size parameter question

According to the wiki page on RSS feeds, the feeds will accept a size parameter "&Size=[size] Where size can be: tiny, thumbnail, small, medium, large or original".

Does anyone know if this supports the new Smugmongous sizes and, if so,
what the names of those new sizes would be? To limit the feed to the XL size, would it be "&Size=XL" or "&Size=XLarge"?

Here's the context of my question. I have a wireless photo frame that works off an RSS feed. The frame itself is larger than the Large image size, so I'd like to feed it the XL size. I can limit the whole gallery to the XL size (that's my work-around for the moment), but I'd rather allow the gallery to be larger, but limit just the RSS feed to XL.