Figured it out.
Had to use
RTMPDumpHelper and attach to iexplore.exe to get the correct parameters.
Also had to add --live parameter because the download would reach a certain percentage and loop from 0 again with an ever increasing filesize
Code:
rtmpdump -r "rtmp://wowzastream-1594986830.us-east-1.elb.amazonaws.com:1935/bnowvods3/_definst_/" -a "bnowvods3/_definst_/" -f "WIN 14,0,0,176" -W "http://cdn2.younow.com/js/jwplayer6/jwplayer.flash.swf" -p "http://www.younow.com/mediaPlayer.php?entityId=19452144&entityType=f&srcId=0&inviteStr=0" -y "FLV:amazons3/younowvideos/2a/d2/842037_19452144_x264.flv?sessionId=e94e5b598300da4d018e4ca6ec8648b5" -o 842037_19452144_x264.flv --live
