For example, if I vary the time to full power between zero and, say, seven seconds, I see very little difference in takeoff distance. Why? Well, it's common sense, really: The airplane is moving very slowly at the start of the takeoff roll, and so it doesn't cover much distance in the first few seconds no matter what you do with the throttle. A rolling takeoff may help you avoid getting bogged down in soft soil or sucking up pebbles into your prop, but it won't make a noticeable difference in where you leave the ground. On the other hand, running up to full power while standing on the brakes allows you to adjust the mixture for best power.