Shipbucket

Personally, I'd revert to the smaller bridge with tripod mast configuration. If you are worried about not having the space to fit the gun director and rangefinder there might be a good compromise:
The one you fitted now, housing in a single unit the Type21 radars and the RDF antenna is the same unit installed on the Agano class CLs, this means a 1942 unit. As mentioned in your opening text this Ibuki was refitted in 1939/40, some 2 years too early. Still, that's just around the main refit cycle for the earlier heavy cruisers (Aoba/Furutaka/Myoko classes), which happened in 1936-1941. This gives you a good excuse to manifacture one (or more) of the type 94 directors that was installed on those ships just for your ship. On the sheet I've linked, is the unit on the 8th line from the top, and it is less space-consuming than the Mogami/Tone ones (and than the Agano/Ooyodo's).

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My Worklist
Sources and documentations are the most welcome.

-Koko Kyouwakoku (Republic of Koko)
-Koko's carrier-based aircrafts of WWII
-Koko Kaiun Yuso Kaisha - KoKaYu Line (Koko AU spinoff)
-Koko - Civil Aviation