Many great positions drills can be written about using a solid center ball hit and just adjusting the speed that you take the shot. This drill will help you understand how speed relates to the rail, when hitting the cue-ball at center.
Using a center ball hit and the right amount of speed is all you need for many shots. Let the natural role of the cue-ball give you the positioning that you need.
Studying the natural angles, and path of the cue-ball after making contact with the object ball will save you the time trying to figure out what type of english to use. A lot of players would try to add some left hand english to a shot like this. It is not necessary and could be potentially harmful.