Get forces along a path in a shell element

Hi! 

I am new to Karamba and currently working on a retaining wall. I would like to retrive the forces acting in the shell element along a specific path defined by e.g. a line or points. 

I have compared the output values of the "Shell Forces" function with the "Line results on shells" function (choosing Isolines). "Shell Forces" is said to output the forces at the center of the faces, however when those points are inserted into the "Line results on shells", the obtained results differ (Principal forces are compared).  

1) Am I thinking in the wrong way when approaching the Isolines?

2) Is there a simpler way in Karamba to output the shell forces along a specific path on the shell?

Best Regards,

Jajjan