Dr9Ball
I conducted this study about two years ago and have used the Z2 since then. As I remember there were about six good trials in each cell. By good trials I mean that I felt that I executed the shot as it should have been executed. No head lift, bad swing, etc. Shots that were not included were excluded before contact was made to insure I wasn’t being biased in my results. The results were for my own use (not publication) so I tried to be as honest as I could be.
To assess deflection I actually used a slightly different methodology. The two object balls on the rail were placed one ball’s width off the rail (measured with another ball). When the cue ball hit an object ball I could measure where the OB hit the rail by tracking the ball’s path back to the rail and measuring the offset. Only measurement freaks (like me)

would be interested in such a detailed measuring technique.
I use Joe Tucker’s description of front and back offsets for the cue stick to play all shots with English. Essentially the back of the cue stick is brought to the center line of the cue ball to reduce deflection. I have been using this technique for several years and think that I am reasonably consistent with it. I attempted to use the exact same off set on every shot.
Of course the original shafts are about 13.5 mm ( vs 11.75 for the Predator) and I tried to take this into consideration when cueing and attempted to strike the cue ball the same distance from center with theh center of the cue tip.
There are many variables and many places for confounding to occur. I simply did the best I could. Of importance to me was the idea that if I had any bias it was to have my original shafts come out as the “better” shafts. At first I was disappointed and rechecked my findings about every month or so. I found a consistent difference of about 30 percent in favor of the Predator Z2. Just could not find a reason to switch back – damn it. After about six months I gave up and left the pretty shafts in the closet.
PS all shafts had LePro tips that I installed at the same time. Now I want you to know I am not OCD but I am a serious pool player ! Over time the Predator had more use and I also found that using the same spot on the Predator with label up did not seem to alter its playing charcteristics over time.
Others my not know and it is worth stating, I am a scientist and it can be assumed that I considered randomized trials, positional efects, time of day, etc, etc. This was a serious study for me but not to be published as it would have required several subjects with several differnt cue sticks, tables, etc. The results were useful to me and are suggestive for others to replicate.