I find the 3pt approach does work. Altho, I have yet to try the endless lighting possibiliities. Did unchecking interpolation remove the problem? Looks like it. Interpolation can be a pain. Once you get it right try an irradiance map...so far it does seem to boost render time if the map is made with nothing to render. Then applied.

No need to think outside the box....
    Just make it invisible.