I agree with lwd, a turret farm is a good explanation.
One of my youthfully favorite ships was HMS Agincourt. Probably still the "King" of throwing shells in one direction. 7 twin turrets of 14 in? all capable of firing broadside...at once.
It was said she'd roll over if she fired a broadside, but this was proved wrong at Jutland where she fired 10-12 broadsides. The rest of the "Grand Fleet" thought she exploded (blew up) every time she did. It must have been quite a show!
The Tone & Mogami classes were both originally designed as Light Cruisers with triple 6.1 (DP) inch guns. Same amount and placement of turrets. To get more boats for the weight/gun, requirements/limitations of current treaties.
Once started (known/observed)(they do take a while to complete), they could be, and were, easily converted to overweight, overarmed (per treaties) Heavy Cruisers. A clear violation, as were many ships in most Navies (especially the IJN).
The Tone/Chikuma were touted as the eyes/ears of the fleet for being able to operate so many float planes. Up to 6, I believe.
There was a problem with having heavy guns firing near float planes/hangers/catapults with collateral damage to the planes from concussion, fire, etc..
Perhaps why Americans chose that middle hull position?
Even Battleship So-Dak had set a serious fire to one of her planes, during a manuvering battle at Guadalcanal. Turned out to be no problem as another salvo blew the flaming plane overboard.
Chikuma/Tone solved that problem by having the main batteries forward. The arrangement is probably to save weight. A Barbette (a tall one), is as heavy as a turret (almost), so keeping them flat as possible, and still having them available in a broadside, will by reducing weight, add speed, and fulfill the semi-original design/purpose of having a fast, seaplane loaded, capably armed CL to CA "Hybrid" scouting Cruiser.
I'll wait for Mr. Gardners corrections
