Suggestions from someone with previous experience organizing events.
1. Decide times and the timebase. I had one event messed up because people got confused about the timezones and what not (also daylight savings didn't help). Suggest using GMT and then people can check against a typical world clock to identify the local time for the event but that's your choice.
EDIT: Oops, that's already being done:rolleyes:...<thumbs-up>
2. One option is to play the same battle at different times of the day or multiple times in a row (say 2-3 times) so different people can be involved. Depends really how spread the timezones are for people participating but if you pick 2-3 different times spread out you can allow everyone in your groups to participate that might not be able to make the one event otherwise. The outcome could then be decided as the best of X. Also avoids the problem of a late arrival entering and changing the outcome of the battle since he can be told to sit and wait for the next round.