anchor.diff:           !!!call Linearize_Point_to_Point( y_ED%PlatformPtMesh, u_HD%Mesh, MeshMapData%ED_P_2_HD_W_P, ErrStat2, ErrMsg2 )
         
            HD_Start     = Indx_u_HD_WAMIT_Start(u_HD, y_FAST)  ! start of u_HD%Mesh%TranslationDisp field
  -      
  -         ED_Out_Start = Indx_y_ED_Platform_Start(y_ED, y_FAST) ! start of y_ED%PlatformPtMesh%TranslationDisp field
            call Assemble_dUdy_Motions(y_ED%PlatformPtMesh, u_HD%WAMITMesh, MeshMapData%ED_P_2_HD_W_P, HD_Start, ED_Out_Start, dUdy, .false.)
         END IF
         
  
positive.code:          !!! ! while forming dUdy, too.
           !!!call Linearize_Point_to_Line2( y_ED%PlatformPtMesh, u_HD%Morison%Mesh, MeshMapData%ED_P_2_HD_M_P, ErrStat2, ErrMsg2 )
        
           HD_Start     = Indx_u_HD_Morison_Start(u_HD, y_FAST)  ! start of u_HD%Morison%Mesh%TranslationDisp field     
           ED_Out_Start = Indx_y_ED_Platform_Start(y_ED, y_FAST) ! start of y_ED%PlatformPtMesh%TranslationDisp field
           call Assemble_dUdy_Motions(y_ED%PlatformPtMesh, u_HD%Morison%Mesh, MeshMapData%ED_P_2_HD_M_P, HD_Start, ED_Out_Start, dUdy, .false.)
        END IF
  
  
negative.code:    
     ErrStat = ErrID_None
     ErrMsg  = ""
             
     ! Add ED Platform mesh to HD PRP Mesh
     !  use Indx_u_HD_PRP_Start
     HD_Start     = Indx_u_HD_PRP_Start(u_HD, y_FAST)  ! start of u_HD%Morison%Mesh%TranslationDisp field     
     ED_Out_Start = Indx_y_ED_Platform_Start(y_ED, y_FAST) ! start of y_ED%PlatformPtMesh%TranslationDisp field
     call Assemble_dUdy_Motions(y_ED%PlatformPtMesh, u_HD%PRPMesh, MeshMapData%ED_P_2_HD_PRP_P, HD_Start, ED_Out_Start, dUdy, .false.)
     
     
     if ( p_FAST%CompSub == Module_None ) then 
        ! dU^{HD}/dy^{ED}
           !...................................
  