I have come up with a new suggestion. This is quite a long shot and will probably not work but I will share it anyway. I have had quite a few of the whole booster boxes. In every box I got three ex cards and they were all in different places each time. However, I have noticed that usually the right hand pile in the box tends to have one ex card and the left normally has 2. So I am not saying this works, but I reckon there is more of a chance to get an ex card if you pick from the left hand pile.