I would wait. If they have had your primary for awhile maybe send an e-mail asking if your file, up to this point, is complete or if they need any other information. They do screen and decline people from filling out a secondary app so it may be a waste of your money and time to complete it before you know if they actually want you to complete it. They will be very honest with you and where you stand in the process if you send them an e-mail so if you're feeling ansty just inquire if they need anymore information to make a decision on your application at this point in the process.