If you haven't already read them, there is slashperverts dirty series. I think 1-3 are just Fred, George, and Harry. 4 is Fred, George, Victor, Oliver, Charlie, and Harry. and #5 (which is called Blind Date) is just Charlie/Harry.
slashperverts profile: http://members.adult-fanfiction.org/profile.php?no=1296805863
D1: http://hp.adult-fanfiction.org/story.php?no=600018990
D2: http://hp.adult-fanfiction.org/story.php?no=600021466
D3: http://hp.adult-fanfiction.org/story.php?no=600021836
D4: http://hp.adult-fanfiction.org/story.php?no=600023566
D5: http://hp.adult-fanfiction.org/story.php?no=600026157