Ken Heard wrote:

> 
> It consequently uses only about 40-45% of the screen area, nor is it
> centred on the screen. It starts more or less from the upper left
> corner and leaves an L shaped unused black space on the bottom and
> right sides.  The left side does not correspond to the left side of
> the screen; a strip on the left side of the display is seen on the
> smaller monitor but not on the large one.
> 

On some graphic cards it is not possible to scale the size per output. 
This means that you are forced to stick to the same resolution on all
outputs. This is great if you have same type of monitors, but not else.
As result you are forced to use the lowest common resolution provided by the
end device (tv, monitor etc).
If you select higher resolution than supported you can either configure the
image to be fixed (so you do not see or use all of the screen) or slide.

However some tv sets provide the option to scale the image to full screen
(look for format and set to custom - usually it is auto). Perhaps this will
be the best for your case.

regards