The sliding the image thing: For some reason, if you don't do this, Poser will do this, and the reflection map will show up with a visible line up the middle. Actually, any reflection map does this, but with most landscape stuff you cannot tell. You can experiment with it easily with a sphere and see what I mean. I found this out while trying to fake raytracing -- the attached image to this shows a shifted reflection map and is rendered in Poser 4.0.3