I'd still use coin flip in an 8 minute overtime. And yes, the odds still are in favor of the team winning the toss, but I think a little less. First of all, unless that team holds the ball for the entire 8 minutes , the other team is going to get a chance to score. Most drives are a little shorter than 8 minutes...especially if each team were giving 2 timeouts which they could use to stop the clock. There's not going to be a perfect system. I think an 8 minute OT would be great. It wouldn't greatly lengthen games, it keeps the intensity level up and urgency to make a stop on the defense or score on the offense.