I had a look at this post (http://www.gravityhelp.com/forums/topic/multiple-user-registration) and this is exactly what I am using, except that I am missing something.
I pasted the code in my functions.php file (http://pastie.org/2339194) and changed the form id to 13. Am I supposed to change something on line 11 too to specify my email field's id?
My form is on http://jfllsa.org/team-registration/