What state and county did the divorce proceedings go through? Would be good to know since different states/counties vary in how they define things.
Should help some.
http://www.winningcustody.com/
Not sure if this will help but i am going to assume that gaining a mountain of evidence without her knowing would be your best bet. Also apparently if you fail at your first attempt to gain custody the second go around will be nearly impossible.
Edit: Social Services would be a good place to start when gaining information on court custody battles. Just make sure to be careful on what information you give them as they will start snooping around and may tip of the mother.
XI Wiki


