Once you have the general design cut out you need to trim all of the excess bits and make the head piece symmetrical.
1. Use a pair of pliers to remove all of the excess rib cut-outs that you don't need. I found that If I grabbed the piece of metal that I wanted to remove and bent it back and forth it would remove it cleanly and evenly.
2. Push the 2 parts of the head together and cut them so they are the same. Also cut a couple of tiny triangles for the mouth on both parts of the head.