VirtualBox VRAM

Is there a way to force virtualbox to setup a guest with more than 256MB video ram?
i have a UHD monitor and this is slow compair to using a VM with FullHD screen
i tried to set VRAMSIZE higher on *.box file but no luck to setup it higher than 256.

 <Display VRAMSize="256" monitorCount="1" accelerate3D="true" accelerate2DVideo="true"/>

virtualbox is version 4.2.x

You can search the VBox forums and find that the VBox video driver does not support more than 256mb of VRAM.

But more to the point, I agree with what is posted there which is that it’s folly to believe that simply adding VRAM (if it was possible) might be expected to improve performance. Much like real world GPU, just throwing more VRAM in the system does not necessarily improve performance. Perhaps more important is the GPU speed, its architecture and any special graphics support like OpenGL.