the shell model using linear element type (S4 & S3) it expanded to C3D8I and C3D6 element in CalculiX. The behavior of linear shell element in bending are known not so good, specifically for S3.
probably, quadratic element type (S8R & S6) with layering could be better. The advantages of CalculiX approach is in nonlinear plasticity and contact. Actually, it’s a truly solid element not a shell.