I agree that since the chalk trail on the CB is so prominent, and obviously indicates multiple hits, the rules should probably mention and allow this type of shot specifically (unless there is clear evidence of multiple or secondary contact during the shot).Interesting video Dr. Dave. No, I would not rule that a foul, but also think that the rule books need to clarify this type of shot as not a foul to avoid the rule nitpickers.
With some shafts (especially those that are very stiff, like carbon-fiber shafts) multiple hits are possible with any extreme spin shots (topspin, sidespin, or bottom spin). With extreme tip offsets, the cue doesn't slow as much when it hits the CB, and if it doesn't deflect away from the ball enough, or if it returns to soon, secondary contact can result. For more info and demonstrations, see the maximum english resource page.Your video made me think of another shot, a level cue with max topspin. I wonder if that also is a foul. I'm thinking that the force hitting the near edge of the cb is what causes the dbl. hits. If so, then it seems a max topspin shot might also. ??? Might not because the cb is going straight forward and the forward speed is not retarded by going down first, but would be interesting to check.
Regards,
Dave