MERGE TWO SMARTFORMS ON ONE PAGE FRONT & BACK

I have two smartforms FM_NAME2 and FM_NAME and I am able to print on front and back on one page using duplex, But this does not work on HP LaserJet 600 M602.  I installed Driver ZHPLJCM1 in SPAD for this printer but cannot get the two smartforms to print front and back instead it prints two pages.  This code does work on another printer but need it to work on the HP 600.  Below is the code, can anyone offer any ideas on what I need to do?  Thanks

         ls_output-tdfinal = ''.
        ls_output-tdimmed = ''.

              CALL FUNCTION fm_name2
          EXPORTING
            control_parameters = gs_control_param
            output_options     = ls_output
            is_packlist_data   = i_packlist
            is_label_data      = ls_labdat
            user_settings      = space.

        ls_output-tdfinal = 'X'.
        ls_output-tdimmed = 'X'.

        CALL FUNCTION fm_name
          EXPORTING
            control_parameters = gs_control_param
            output_options     = ls_output
            is_packlist_data   = i_packlist
            zle_ps_header      = ls_header
            is_label_data      = ls_labdat
            user_settings      = space
          TABLES
            text_lines         = lt_text_lines
            vbpa               = lt_vbpa.