There is a great article on arrow balancing on the home page of this site.

http://www.bowhunting.com/everythingarrows.asp?page=5

According to this article correct foc should be between 7% & 10%. My set up if I remember correctly is about 13% foc. I read somewhere that with carbon arrow you acutaly want a higher foc. This may or may not be correct but I'm sure if it's wrong someone here will be sure to correct me.

Hope this helps.