If you jump, you must use your regular playing cue.......... you cannot switch to your break cue................
I can't find a reference in the APA handbook to dispute it, but I can say for a fact that I watched a 9ball singles match in Vegas for the black tier (6-9SL's at the time) and one player switched to his break cue to successfully make a jump shot and they allowed him to continue shooting without questioning him.
The guys playing were both ranked among the top 10 APA players nationally (I mean "ranked" in the loosest sense since players aren't actually publicly ranked or seeded going in to the tournament) so needless to say the match was pretty popular and had a large group of people watching including 2 APA ref's donning their official APA "red smocks" and not a single person, officials included, questioned the player who switched to his break cue to execute the jump.
Maybe the players agreed b/w themselves (although I doubt it) beforehand or maybe the officials were so bored from watching a lot of mediocre pool over the course of the week that they didn't think it was worth intervening since the opposing player didn't question it. Either way I can only describe what I witnessed.