I'm going to six flags soon and I've gotten a season pass and so has my friend. I'm planning on bringing 4-6 people. Is it possible to use more than 1 bring a friend for $15 per passholder? Or if there is only 4 of us, me and my friend will just use the bring a friend for free on the other 2 people. But can you use more than one $15 coupon? Thanks!