With the addition of APCBC shell for Sherman tank, Chi Nu will be less viable against Sherman due to the need of aiming certain weak spot while Sherman can pen it basically anywhere from the front and do a lot of damage.
So Japan need a tank like the German long barrel panzer4 on br3 to counter Sherman.
Chi Nu II is the best candidate for it. It has only 50mm of frontal armor and a main gun that is comparable with long barrel panzer4.
