I see a lot of pictures on forums of guys wearing their plate carriers with armor in them in ways that barely do them any good all the time. Usually you see the plates setting too low in the front and the back. As can be seen in this picture you do not really need a huge plate to cover every inch of your body, but you do need it to cover the most important inside red parts.
Here are a couple of pictures I hope will help people make sure they do not wear their armor wrong and some day have a round slip through or over a plate and cause sever leaking.
These pictures came from a poster on http://www.ar15.com