Rooster or Hen?

This is the timeless question for the "unsexlinked" breeds.  Everyone always wants to know if a chick is going to be a rooster or a hen.  We have read lots of information and watched numerous videos and I think I've come to the conclusion that it is a skilled art. :-)

A friend of mine sent me this from Mother Earth News.  The picture below is from this link: http://www.motherearthnews.com/multimedia/image-gallery.aspx?id=64556

This is their theory and I'm not sure I agree with it or not as our Black Sex Link always lays very rounded eggs and I can hardly believe that she only lays females.  My Blue Copper Marans pullet, on the other hand, always lays a longer, more oval egg...I'd be devastated if she only produces males!


What do you think?  Anyone have any thoughts on this?