The Ki84 shares with the P-38 a noted reduction in elevator control when using combat trim.
Don't use it with the Ki84. You can barely pull blackouts with it on, but can quite easily with it off. That alone tells you it's severely limiting your input capabilities.
Definitely an excellent plane. Takes some getting used to.
I've landed 7-kill sorties in it before, sniped running la7s at 800 yards with just my cowl guns (cutting a wing off too!), out-spiral-looped P-38s, etc, in it.
Too many folks run away in the MAs, so I've fallen out of flying the Ki because it can't chase. It's got a nice fast deck speed when level, but it can't dive worth a crap without losing all 5 flight surfaces at once. That's the only reason I don't fly it more.