Apparently I am. While everything worked fine using Firefox it didn't work at all in IE. I was a little bit floored to say the least. Usually IE is much more forgiving.
Passing the content to be displayed in the iframe's page through the query string didn't work for IE - I don't know if it was an issue with the content being to long or not. It just wouldn't display the iframe in IE, which I thought was weird.
It worked out well and is apparently the “right” way to do it. Guess I should have just done it right the first time instead of looking for a shortcut, huh? You live and learn.