The third turret location is in the direct rear of the ship, which allows all three turrets to focus fire enemy ships that are directly on your tail. While maneuvering in a dogfight, you can expect that at least 2 of the turrets can focus fire on the same enemy at the rear. The top turret location has been pushed further aft to allow for the new cockpit location, so it doesn't have as clear of a fire arc to the front as the original Durston has. That said, maneuvering to face a new target so that the top turret can shoot is still the ideal tactic.
The gun hardpoints are also located in different spots than the original Durston. Two are centered directly below the cockpit, and the final two are mounted along the starboard side of the hull, leading to a slightly less concentrated fire cluster than the original Durston.