There is no way to only let the leader and/or seniors see the formation, but if u have people spying in ur group u always win, trust me. Just change the formation last 20 seconds or so and ur done. First u do the wrong formation and then plan with the seniors who moves which battlefield and so on. Each time u do other formations so they can't find a way to counter it. Since we do that in our group and only came 2nd in 1 time and the rest of the timese 1st with the leader we have atm, I c*most confirm that it works... There c*ways be unlucky times when they put the formation just right countering the one u had atm. Even if u think there are no spies in ur group, still do the tactic, cuz u never know :)