I would use engine rpm over MPH. While MPH is nice to know, a specific MPH and throttle position may not result in a feasible engine rpm before or after the shift. MPH and throttle position alone just will not tell where engine rpms will be which is far more important than the MPH itself. Your engine has a power band and optimum acceleration rate within a specific engine rpm range, not a MPH range, whether striving for peak performance or not. Just my two pennies on it.