I have no signed custody agreement in place and it is working fine. Of course we are only a couple of weeks into the separation, but I don't anticipate any problems at this point. I intend to continue on like that UNLESS problems do start and then I will go the route of getting something in writing. So my advice is if you think there's a reasonable chance she is going to play fair then leave it informal. If you start getting conflicts then get something in writing.
