In my oppinion, transport turrets suffer from being very very tall.
Their size, in porportion to even the trains and 4k+ transports, is quite significant, and because of the way they protrude from the ship, they take away from the aesthetics of the ship.
So scaling that gun to the current size of the transport turrets makes for a very large protrusion.
I think you should consider building much smaller/more compressed housings on the turrets.