I'm trying to convince my parents to let me get my septum pierced, any suggestions?

I’m nearly 16 and my parents are fairly cool. They let me dye my hair funky colors and even said I could get a nose stud. Unfortunately septum is another story. The thing is, I think a septum piercing is pretty brilliant. I mean, it’s extremely convenient to hide (a nose stud not so much). So, I’m in need of some tips for convincing them that a septum piercing is the way to go.