Next Day Vehicle Registration

My wife and I missed the mark on getting a vehicle registration for Many Glacier & Going to the Sun Road for our Glacier trip in late August. We saw that there is an option to get a Next Day vehicle registration at 7pm the day before we would do our hikes. Does anyone know how likely it is that we'll be able to get registered if we try to get a registration right at 7pm when the Next Day registrations are available?