Transmission and reflection : Combine front and back reflection for DoubleSided (not with forceSinglePass)

Hi all.

I read in the doc of MeshMaterial that, for double side meshes, the transparency in draw in two call (if not forceSinglePass = true)
I wonder if it would be possible and how could I combine the front and back face reflection of the geometry int his case to obtain a transmission effect that in clude back and front reflection.
If it’s possible, the idea would be not to create instance or clone but use the existing and, perhaps do it with a specific parameter or addin onBeforeCompile code ???
I’m open to all your ideas to do that…

Thanks at all !