I personally don't have a sorority tank, but I do want to start one someday. Which means that while I have been a member on this forum, I have subscribed to a few threads on the subject... ;-) I looked back through and here's a couple of links to the ones that might be helpful to you. Hope these help!
Important tips to a successful sorority:
http://www.bettafish.com/showthread.php?t=123796
Female Betta Sororities:
http://www.bettafish.com/showthread.php?t=29402
Important tips to a successful sorority:
http://www.bettafish.com/showthread.php?t=123796
Female Betta Sororities:
http://www.bettafish.com/showthread.php?t=29402