FSSO WebFiltering more than 5 group of users

Hi, my boss told me to profile every office to permit/deny web traffic. In total we have 7 departments (example commercial, marketing, export.....) I start to profile every office by a group on the domain controller and to add the relative Single Sign-On on the firewall but i found that the max of FSSO that i can create is 5. http://help.fortinet.com/.../5-2-4/max-values.html Now i've tried to create a Firewall group with remote groups but the user authentication is explicit required for navigate and not automatic like the single sign-on. There is another method to profile more than 5 group of users?

I hope i have explained my problem properly.

Thank's