Let's just admit it, this is entirely because I'm 116 turns into a playthrough of Rome Total War 2, and I've discovered that artillery ships will eat transports alive (and also serve as a good way to grind out Heroic Victories, if you need any).
In the course of mucking about with onager quinqueremes, though, my mind went back to the appropriate Wikipedia page. Which leads me to the question: Where do we stand on number of oar banks and/or men per oar regarding the warships of Rome 2? Are we still thinking of the quinquereme as a trireme with extra rowers on the top two files (ie, the 2-2-1 arrangement)? What do we think of Lionel Casson's posited one-bank quinquereme (ie, one oar, five men per oar)?
While we are better informed now about the size of Roman warships, thanks to the discovery of the Athlit Ram (probably a four), the Egadi Rams (threes) and William Murray's work on the ram sockets Augustus' victory monument Nicopolis, which once housed the rams taken from Anthony and Cleopatra's ships at Actium (these included a number of very large polyremes, probably 7s and above).
While there has been little new evidence on warship layout (hard to reconstruct from rams), the consensus now is overwhelmingly that most polyremes had three banks of oars, and that the number that gave the ship its name referred to the number of rowers on each bank, so 2-2-1 for a "five".
Probably the most up to date book is William Murray, Age of Titans: The Rise and Fall of the Great Hellenistic Navies (Oxford 2012).