Per my previous post, I HAVE done a careful experiment to test for this using a marked Meucci flat-laminate shaft (which should have even more of a "spine" than a non-laminated shaft). Again, I saw no difference in squirt (CB deflection) with different cue orientations. For the detailed results, see Diagram 3 in "Squirt - Part VII: cue test machine results" (BD, February, 2008).Noone so far has tested deflection based on the orientation of the spine of a maple shaft which is supposedly what the red dot denoted... I doubt that the players of old who knew how to mark the spine didn't have a reason even if noone understands why.
Again, for more info concerning why spine orientation should have very little or no effect on squirt (CB deflection), see:
what causes squirt?
endmass and stiffness
The "hit" and "feel" of a shaft might vary with orientation, but both experiments and theory agree that stiffness differences with orientation should have no practical effect on CB deflection (squirt).
Regards,
Dave