Yes, the 8-inch guns are longer than the 6-inch ones, so B (2) turret cannot lower the guns below 12° or they would struck the roof of turret A (1)
And here is the 1938 Mogami, she was still a light cruiser armed with 15 6-inchers back then, but major works where already implemented to correct the stability issues (fiting of bulges mainly, but also modifications on the catapults area and the fitting of a lower mainmast (you will see the difference once i will post the 1935 version of Mogami).
Main guns comes from ALVAMA's Yamato (as the battleship mounted the very same turrets removed from the Mogamis during the CL/CA conversion with minor modifications), but (there is one, sorry Lad
) they where 6 pixels shorter so i lenghten them to get the proper dimensions; their proportions where correct and the drawing was good, they just lacked some lenght in the back.