Following the fresh flash needed for 156 onwards, the VU XBMC (Gotham) plugin no longer seems to work in full screen, rather it's a smaller 'window' top left of the screen.
Looks like it might be related to the 1080p framebuffer stuff, and therefore the issue could fall in the VU Drivers, the VU XBMC plugin, or Openvix itself - it's not easy to determine, so wanted to raise it here. Issue has been confirmed by others in the XMBC section of the forums, on different VU devices.
I've also tried going back to a non-1080 skin, launching from an SD channel with auto resolution enabled, but nothing made a difference.
It did work fullscreen prior to the fresh flash for 156.