What you are describing is exactly how duplex is supposed to print. To do what you want, you need to do something different like this:

*-- Print the report for all records
lnCount = RECCOUNT()
FOR ln = 1 to lnCount
  REPORT FORM rpt_notice_fl RANGE ln,ln TO PRINTER NOPAGEEJECT
  REPORT FORM rpt_notice_fl_back RANGE ln,ln TO PRINTER NOPAGEEJECT
ENDFOR

*-- End the print job
REPORT FORM rpt_notice_fl NEXT 0 TO PRINTER