Force Virtualbox Display in Fullscreen

I have a dual display setup with virtualbox.  In fullscreen I found that virtualbox would switched onto my smaller display.

This can be adjusted.

1) Switch to fullscreen with Virtualbox

2) Use the combination of your "host" key + "home" key. (right-ctrl + home) in my case.

3) Go to the "view" menu item -> "virtual screen"

4) Select the appropriate monitor.

5) If the size of your display varies,  you will have to go out of fullscreen and back into fullscreen to re-adjust the workspace to the correct size.