How can I apply the electrical loss caused by back shading ?

[Lunatic09]

I simulated bifacial PV system with tilt : 90 degree,  Azimuth : 135 / -45 degree  (same position but facial direction different)

I set the parameter of back shading of azimuth 135 degree to near shading loss value(obatained from 3D simulation) of azimuth -45 degree. 
The opposite case was carried out in the same way.

As comparing the results (attached image), "shading : Eelctrical loss detailed module calc." looks the loss only effected by the near(front) shading losses.
In case of back shading loss is high and near shading loss is low, value of "Shading : Eelctrical loss detailed module calc." is low. (left loss diagram attached image)
Q. How can I apply the electrical loss caused by back shading ?