I'm using corona from 4 months already but I still did't figure out how to achieve the same results I had with the VRay 2Sided material.
The material essentially allows seeing the light on the backside of objects and allows to have 2 different materials for each side.
It was perfect to simulate thin translucent surfaces like paper, cloth, curtains, and tree leaves above all.
It would be great having something like that in Corona!