Well, last night I found a solution that worked for me… But I had to stop using that Nvidia cubemap generator, since I couldn’t get that working, and I couldn’t get Spacescape to export to the right format, so that the sides of the cube actually lined up.
I finally had to get AMD’s CubeMapGen program, and Manually import all 6 files onto the right sides of the cube/sphere in that. Actually didn’t have to do much rotating at all, then just saved as a DDS with that.
For some reason, UE4 seems to have better luck using the CubeMaps from the AMD tool, at least for me. It imported into UE4 perfectly, and it worked fine with the material script you posted above (tho I didn’t need the divide node).
Also, I had to tweak some of the color settings of the Cubemap in UE4 to make it look right, color wise, but that didn’t take too much playing around.