Only downside to the non-double sided, is that it doesn’t show the shadows of the wall bump :S but it is a drastic improvement over the ghosting…
There is one more solution that I ended up trying which… gives the best result, actually making a double-sided mesh of the wall hah…
the thick wall doesn’t have ghosting problems, nor does it need to have double sided material, and keep the shadows.
thanks so much for your help though, definitely a good thing to know moving forward on how the materials & raytracing affects the mesh!