I've just installed a Samsung (55KU6400) 4K TV, linked to a RX 470 via HDMI 2.0 certified cable. The image is OK running at 3840x2160@59Hz.
Once I set the res to the native settings (4096), the display is rendered inches bigger than the panel and there's no option within the Crimson drivers to fix this.
Also, the VGA insists in setting the refresh rate to 59Hz instead of 60Hz (native).
I'm using the latest Crimson drivers.