Changing the values you mentioned appear to make no difference, even changing it to position:static produced the same result.

 

I would imagine that this would be easily reproducable if you render the editor in a div that is absolutely positioned. Clicking on the full screen button displays the layer about 16 pixels to the top left of the original div and sticking out over the bottom right of the screen.

 

Full screen should really display the layer all the way from the top left to the bottom right of the screen.