The best way to increase hop flavor is to use a hop stand. Use just enough of a smooth bittering hop at 60 minutes to get your target IBU's, then add all your flavor hops after flameout once your wort gets down to about 170F. Stir the heck out of it, then let it steep at that temp for a half an hour (stirring occasionally) before chilling the rest of the way and pitching. You will be amazed at how much hop flavor you will get. There is no need for a hopback, this works way better.