The other thing to keep in mind is that the posted wait times are often inflated, especially at the end of the night and leading up to parades/fireworks. From what I've seen, people who have FP+s for an attraction tend not to use those during the parades and fireworks, so the SB line moves very, very quickly from about 20 minutes before through the event. Once the parade/fireworks are over, the SB line comes nearly to a stop while the FP+ line is swamped. So your timing has to be good, too.