Keyword Feeds: Multiple Keywords?

photokandy

I'm using the keyword feed for my front page slideshow. I'd like to be able to use, say, "nature" + "portfolio". So, I naturally assumed I could make my feed url like this:

http://sm.photokandy.com/hack/feed.mg?Type=userkeyword&NickName=photokandy&Data=nature-portfolio&format=rss200

Well, that doesn't work -- when I view the url in Chrome, I get this (instead of the expected feed):

This page contains the following errors:
error on line 2 at column 1: Extra content at the end of the document
Below is a rendering of the page up to the first error.
(big blank space)

I've tried just about every special character I could think of instead of a dash, and continued to get the same error. I finally had to drop the extra keyword, and then it worked perfectly.

At the moment, I'm left with the thought that I'll have to go through and tag those images containing the combination of keywords I want with a new keyword, and use that. And I can do that, but I was hoping that the feeds could support that naturally.

So - thoughts? Ideas? Am I missing something? (I'll admit -- this was late last night, so it is entirely possible!)

Thanks in advance!