which does affect the calculation.

this is very bad. But how do they influence? I made a test model, with offset and without the result was the same

When the solid cylindrical wall has a Midsurface operation, that pulled the surface away from the solid on the inside. The solid on the inside will not be connected to the wall once the geometry is opened in Mechanical. 

- this is my question, do I need to extend it to the shell? for example, a pull tool in the SC.