anchor.diff:     ! --- Reduced vector of external force
      if (p%reduced) then
         m%Fext_red = matmul(transpose(p%T_red), m%Fext)
  -      UFL= m%Fext_red(p%ID__L)
  +      F_L= m%Fext_red(p%ID__L)
      else
  -      UFL= m%Fext(p%ID__L)
  +      F_L= m%Fext(p%ID__L)
      endif
  +
   contains
      subroutine Fatal(ErrMsg_in)
         character(len=*), intent(in) :: ErrMsg_in
         call SetErrStat(ErrID_Fatal, ErrMsg_in, ErrStat, ErrMsg, 'GetExtForce');
      end subroutine Fatal
   END SUBROUTINE GetExtForceOnInternalDOF
  +
  +!------------------------------------------------------------------------------------------------------
  +!> Construct force vector on interface DOF (I) 
  +!! NOTE: This function should only be called after GetExtForceOnInternalDOF 
  +SUBROUTINE GetExtForceOnInterfaceDOF(  p, Fext, F_I)
  +   type(SD_ParameterType),   intent(in  ) :: p ! Parameters
  +   real(ReKi), dimension(:), intent(in  ) :: Fext !< Vector of external forces on un-reduced DOF
  +   real(ReKi)            ,   intent(out ) :: F_I(6*p%nNodes_I)          !< External force on interface DOF
  +   integer :: iSDNode, startDOF, I
  +   DO I = 1, p%nNodes_I 
  +      iSDNode = p%Nodes_I(I,1)
  +      startDOF = (I-1)*6 + 1 ! NOTE: for now we have 6 DOF per interface nodes
  +      F_I(startDOF:startDOF+5) = Fext(p%NodesDOF(iSDNode)%List(1:6)) !TODO try to use Fext_red
  +   ENDDO
  +END SUBROUTINE GetExtForceOnInterfaceDOF
   
   !------------------------------------------------------------------------------------------------------
   !> Output the summary file    
  
positive.code:       m%udot_TP    = (/u%TPMesh%TranslationVel( :,1), u%TPMesh%RotationVel(:,1)/)
        m%udotdot_TP = (/u%TPMesh%TranslationAcc( :,1), u%TPMesh%RotationAcc(:,1)/)
  
        ! Inputs on interior nodes:
        CALL GetExtForceOnInternalDOF( u, p, m, m%UFL, ErrStat2, ErrMsg2 ); if(Failed()) return
  
        !________________________________________
        ! Set motion outputs on y%Y2mesh
  
negative.code:       INTEGER(IntKi), pointer      :: DOFList(:)
        INTEGER(IntKi)               :: startDOF
        REAL(ReKi)                   :: DCM(3,3)
        REAL(ReKi)                   :: F_I(6*p%nNodes_I) !  !Forces from all interface nodes listed in one big array  ( those translated to TP ref point HydroTP(6) are implicitly calculated in the equations)
        TYPE(SD_ContinuousStateType) :: dxdt        ! Continuous state derivatives at t- for output file qmdotdot purposes only
        INTEGER(IntKi)               :: ErrStat2    ! Error status of the operation (occurs after initial error)
        CHARACTER(ErrMsgLen)         :: ErrMsg2     ! Error message if ErrStat2 /= ErrID_None
  