IIRC the BGSize entry is the size of the original background texture file, in this case 128x128 pixels. The BGScale entry multiplies those dimensions with the number entered. So a scale factor smaller than 1 reduces the displayed size of the Tactical Display, a higher number will enlarge it on your screen. Don't be afraid to experiment a bit.
Since CFS3 requires textures to be a power of two (64x64, 128x128, 256x256 etc.), and the scale factor affects both height and width, I can't see how it would be possible to stretch the Display in one dimension. However, if you want, you could create a new background texture with a different visible area: The current Display has a circular visible area, but if you'd change that to something else, you might get what you want. You would need to create a new tactical_display.dds which includes an alpha layer that masks the area you wish to be visible.
