I think if you cycle through the picture display options on your Samsung, there should be a "zoom" mode that does not stretch or distort the picture to fill the screen. I know my Samsung has that setting, which I occasionally use if I watch a letterboxed movie on IFC or the Sundance channel. There is some loss of clarity of course, but it's a non-HD channel anyway, so sometimes I prefer to fill the screen.
In a somewhat unrelated comment, up top when you mentioned setting your Pioneer to a non-progessive (interlaced) output, it doesn't matter because your Samsung will de-interlace the incoming interlaced video from your Pioneer if the Pioneer is set for an interlaced output. The question is: which de-interlacer does a better job? Your Pioneer or the Samsung? There may be no difference.
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