Edit > Preferences > General > uncheck "Default scale to frame size"
For a clip already in use, right-click on it in the sequence and uncheck "Scale to frame size."
Hmm, that's already unchecked!
Ah, brain lapse...
Even though your HDV clip's dimensions are 1440x1080, at full raster, that's actually 1920x1080. So, your 1600x1067 file (presumably with square pixels) is going to "float" in the middle of your program monitor. You'll have to scale up or redesign your graphic to be at least 1920x1080 with square pixels (or 1440x1080 with a 1.333 PAR) to fully fill the screen.
Note that you can't just interpret your 1600x1067 with a 1.333 PAR--well, you could, but you're going to get stretching distortion.
Ok, thanks for that, I get it now!