It didn't tell you why the front top pieces were longer than the back pieces either, or how to fasten it all up but I worked out to put a zipper in the side as I got stuck in it when I tried to put it on without. Also it only came in one size, and I had to hope it would fit- it is online as a pdf which you can only print out fullsize with photoshop, so my friend managed to turn it into a paint document and I printed it out that way but there were no measurements on the pieces.
Still I think I pretty much rock it! Of course. Now I'm not suggesting you say I look like Grace Kelly, just that you think it. :)