Protected Opponents Disabled

I am trying to start a team builder dynasty and I recreated my high schools conference. I moved some other teams out of the conference (Big 12) and put them in another conference (Pac 12). The Big 12 has 8 teams now and the Pac 12 has 10 teams. Is there a minimum number of teams needed for each conference in order to have protected opponents? It does not give me the option to turn protected opponents on for the Big 12