Overscan adjustments (backporch timing, etc) are needed only for analog video signals unless you have a very poorly designed HD TV.
As an example, I have a Vizio 24" 1080p TV. When I connected my 1080p FHD laptop to it using VGA, there was a slight overscan. Just enough of the Windows desktop was missing around all four edges to be annoying. When I switched to displayport/HDMI, it became pixel-perfect. Now there is no overscan at all and I can see the entire desktop. It fits exactly within the TV's bezels. Although I previously had the impression that the VGA display was excellent, the computer's graphics now are noticably sharper since the pixels sent from the computer exactly match the pixels on the screen.
Edited to add:
Just to clarify: VGA signals are analog, although you probably were aware of that. My laptop's HDMI connection is getting to the TV by going through a Marantz nr1501 receiver, providing very good 5.0 surround sound. (I happen not to have a subwoofer in that room. It would have been too inconvenient due to space limitations. There's one on the system in the living room, though.)