The Fukada Tree is an "original" sized decca tree array, but with five cardioid microphones and two additional omnidirectional microphones as outriggers to blend in between front and rear channels.
by Akira Fukada, Japan
The choice of cardioid microphones improve the channel separation and the backwards oriented rear cardioids will also minimize leakage of direct sound to the rear speakers.
Omnidirectional microphones are often preferred in decca tree configurations for music recordings due to their natural sound color and full frequency bandwidth. The two omni outriggers serve this very important component in this array.
From the outset, Akira Fukada specified DPA microphones as best suited to his Tree; he insists on using DPA mics for their transparent feel.