Retrieve stresses in shells

I wish to retrieve the stresses in the outer fibers of a shell where both moments force and normal forces are acting. 

I have tried:

1) Using the shell view. I assume this SHOWS the principal stresses in the outer layers of the shell, but it is not possible to extract the actual data (unless I start mapping the colors of the mesh to numbers... )

2) Use that stress =F/A + Mx/I. I can extract the moments and forces from the shell forces component. However, the axes for the principal moment M and the principal force are different.

What am I missing here??

Hope you can help

Best 

Timo