Dear Kurt,
Actually, in FAST v7 it is possible to enable a DOF at run time. For example, adding “DOF_Flag(PtfmSg) = .TRUE.” to the source code will enable the platform-surge DOF even if PtfmSgDOF is set to False within the platform input file. Variable DOF_Flag() and PARAMETER PtfmSg are stored in MODULE FAST_Mods.f90/DOFs(). You can also control the other platform DOFs (via PARAMETERS PtfmSw, PtfmHv, PtfmR, PtfmP, PtfmY) in this way.
More information (with the specific example of enabling/disable the rotor-teeter DOF at runtime) is available in the following forum topic: Blocked teeter.
Please note that it is not possible in FAST v8 to enable/disable DOFs at runtime in this manner.
Best regards,