I'm not sure if there's really any advantage with doing $0 IBR payments, unless you plan to aim for the 25-year IBR forgiveness. But if you did $0 REPAYE, then your interest will be effectively halved during those payments (the gov't subsidizes half your unpaid interest). That's the route I would go. I am not sure if you can start payments until you use up your 6 month grace period however.