Craig, that is a good tutorial but I think it might be aimed a little high. It takes a while to get to the part that the original poster needed to hear. I put a tutorial on my tutorial site that might help.
http://www.stevengotz.com/my-tutorials.html
I used an uneven green screen clip to better help the example. The stage I put the ballerina on is not exactly the one I would have chosen had I an actual choice, but http://www.VideoBlocks.com came to the rescue with the dancer and the stage, so I used what they had.
I have yet to figure out how to link directly to the part of the page I want to show people, so here is the YouTube link.
From what I can see of the original posters YouTube example, the pedestal is probably the main problem.