How to Compensate for Overscan?
 

I have an ACCELL USB to HDMI adapter and with the Mac Driver 1.7, I am experiencing overscan when connected to a Samsung LN-S4092D TV, in that I can't see the menu bar and dock if this is the primary screen

If I connect directly from my Mac mini, the Mac OS X Display System Preference has an underscan slider, so I can compensate. I also see that the Windows driver has a Fit to TV feature which can address this. However, I see no way to do this with the Mac driver.

I've experimented with tools such as SwitchResX, trying to create a custom resolution by increasing the shelf values and decreasing the resolution, but it keeps rejecting them as invalid.

What can I do to get a correct resolution?

Had same issue. Fixed it by changing settings on the monitor itself.
Under "Setup and Reset" menu change PC/AV to PC.
No need for SwitchResX.