If you have a large group (approximately 100 people) and only have flashes, where would you position the flashes to best light the group? It's an indoor stadium with reasonable levels daylight (e.g. could manage f5.6 @ 200 with iso3000 with the sunlight alone from the opague panels in the roof). So the lighting is primarily for fill. However, I only have flashes (2X580EXII and 1X600 EX-RT). I would prefer to drop the ISO level if I could (shooting with a 1D4). I am also concerned about the shutter speed as I have noticed that with movement from the group (e.g. hand waving) there seems to be motion blur in the past (just shooting with one flash on camera in Av mood at 1/125).

I was thinking of having 2 flashes off camera and one on camera. Should I position the 2 off-camera flashes at either end of the group and aim the flashes at the opposite end of the group to each flash; or should the two off camera flashes be placed on either side of me, and aimed at opposite ends of the group? Or should the flashes be aimed in some other direction (e.g. straight ahead). Is it OK to have one flash on camera, or do I really need to buy a 3rd stand. (I am trying to minimise set-up time as well). Lastly, how high should the flashes be placed (e.g. aimed at the height of the middle or back row; or up as high as possible and aimed down at the entire group)? Thanks!