Create Edublogs style signup page - antisplog + Pro Sites

I am trying to create a custom signup page on my wordpress multisite - my aim is to get something very similar to the EDUblogs sign up process. I have read several threads about creating something similar to the edublogs signup process, but can't figure out some of the basics. Firstly, I don't want to use /wp-signup.php as the url for users to sign up by. I'd rather have /signup. I have started by copying wp-signup.php to my wp-content folder and renaming to custom-wpsignup.php (this is so I can work on creating a custom signup page) - however, what is the url to find this custom page?