and even if u aren't using jpeg skycube, im afraid the image ingame isn't any higher res than the skycube (based on the screenshots). think about it this way: by default u hav 60 degree vision, which is a sixth of a full revolution. each side in a skycube takes 90 degrees of vision, or one quarter of a full revolution. basically with default fov, u r always gonna be zoomed into the skycube by a bit. that is less than 512x512 pixels being scaled up to fill ur whole screen with the resolution u r using.

julz