But rigid forces the solid cross section to move as one, right? Thus it would add artificial stiffness. I tried both rigid and deformable. The normal z-stress with deformable is very close to the analytical result (57.3 MPa for a force of 3 kN, a diameter of 20 mm and a distance of approx. 15 mm from load to end of solid), while the result with rigid is almost twice as high.