Dear @Tudor.Istrate,
The StC_DOF_MODE = 5 option of StC requires that you customize your DISCON controller to specify the StC forces, which can be based on sensor feedback that is already sent to the DISCON controller. Are you already using a DISCON controller, such as ROSCO, the NREL 5-MW baseline controller, or your own controller? Have you tried to modify this controller to specify the StC forces?
Best regards,