The antonyms for the word "more flatout" include timid, cautious, deliberate, measured, and careful. These words imply a slower pace and deliberate action, rather than rushing ahead with enthusiasm. To describe someone as timid, for example, suggests a lack of confidence and a reluctance to take risks. Cautious and measured both imply thoughtfulness and attention to detail, while careful suggests a higher degree of concern for potential risks and consequences. These antonyms all convey a sense of caution or restraint, rather than the exuberance and energy suggested by the original phrase "more flatout.