You mentioned that before. I also ran into issues with this for example the island surrounded by water renders I posted a few pages back.  One of then due to the sunlight being in the back the front of the characters leaving the front too dark. I added a curve light ponting upwards at them.

Problem then was the curve lights reflections always looked powder like that never cleared up after 10 hours plus.. I resolved it by removing the curve light and re directing the sunlight.  I ran into this issue with adding a mesh light to IBL as well.

I strongly suspect that I run into these issues due to sometimes needing to alter character's sizes due to my concept so I prolly need to just find what works. With the cockpit renders everything was at their defult size.

 

Mind you I am not a photographer..