Well that seems to have worked. I have to experiment with TGA files to make sure I'm doing everything right though. I pretty much wanted a blank image for the scope view so that the optics wouldn't be blacked out anywhere. That's easy enough to do, I guess I should make sure I save my original TGA files correctly if I plan to do anything more difficult.
If I got this correctly, in the gunner's sight, there are two images. The first is the crosshairs, and the second is the scope.