Ollie I applaud you for always trying new things.
Contests of any kind would be a regular crowd killer for me. I think it depends on the venue. It seems to work better for venues who don't have a regular crowd, but a new influx of people every night or a bar that doesn't rely on just karaoke to bring in their crowd. If you don't need the crowd that would come in for a contest to show up again I believe it would be fine. Contest people tend to show up just for the contest.
Good luck with what ever you decide.
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~*~ MONKEY BUSINESS KARAOKE~*~ [/shadow][/updown][/glow]