by Vera H-C Chan Four remain on " American Idol ," which means the time for projections will soon be upon us. And right on cue, what has become the singing competition's tradition: a carefully planned upset. How to plan an upset The producers may not be able to figure out how to keep its audience from fleeing, but they have some savvy in influencing the results. For weeks, the judges couldn't ladle enough praise upon frontrunner Crystal Bowersox ,