Help Needed to prepare for 1/2 mile Open Water Butterfly

Three of us have been preparing to swim a 750 meter open water race butterfly. We have been training for the past 2 months and will swim the race on August 1st. We have run out of ideas for workouts while trying to keep the fly distance between 1,500 and 2,200 in a one-hour workout of around 3,000 yards total. Does anyone have any great ideas? I beat the overall winner of the tri by 3 min in the swim last year and he beat me by a 1/2 overall.. (Yes the grand piano falls on you while you are out of the water as well as in!) So I came up with the hair-brain idea of trying to beat him doing fly. Worse, I convinced two other people to join in the fun.. HELP PLEASE! If your going to Tri you might as well Fly! Charlie