I was surprised to learn that "Vaulting Ambition" supposedly gives some weapons specs on the Defiant, not even "redacted" at that. But didn't I hear them establish just two forward tubes and one aft?
Kirk's ship definitely had more forward tubes, for a total of six at least (possibly but not all that probably including his canonically unmentioned aft ones).
Then again, this is a perfect opportunity to assume that ships around the 1700 registry are of a different variant than ships around the 1760 mark. Many fan works go with two forward tubes, in the top superstructure, because of what Franz Joseph once speculated upon. Now, we know NCC-1764 has at least one forward tube in the usual location at the bottom of the saucer, blasting at opponents in "In a Mirror, Darkly", so she's not of the FJ variant exactly. But we could still go by the "batches with more or less consecutive registry numbers" model here.
Anybody got a good closeup of the Defiant files?
Timo Saloniemi