Hi, tommorow i need to shot a group of 8 people, in a line. at a local stadium. the day will be overcast, and naturally lit from above. but it may be a little dark in there. i think i will need to use fill flash..would that be a good idea? also what f stop would i need, to keep everyone in focus? i'm shooting with a canon 350d, with a sigma 2.8 20-40 lens. any help would be much appreciated.