Why is it usually recommended to have the forearm perpendicular to the cue at CB impact?
With a non-elbow-drop stroke, and with the forearm perpendicular to the cue, the cue tip will be moving exactly straight in the cue direction. If the grip is forward, the tip will be moving down into the ball; and if the grip is back, the tip will be moving up at impact. Also, there is a natural tendency to reach a constant maximum cue speed when the forearm is perpendicular to the cue at cue ball address. This can make it easier to control your shot speed, because the speed of the cue won’t be changing much just before contact. For more info, see: