Down on the stick may not be indispensable but it affords the best view of the front end of the stick and cue ball and equally important, the eclipse of the object ball; all this while providing the most stable shooting stance there is.An interesting gadget. The same could be accomplished by stroking the cue stick between two object balls at the table--especially since I'm not convinced everyone needs a low chin or even to cue on their chins.
I hear what you're saying, I also have older students with back and neck pain trying to still emulate the younger dudes and gals. Even a foot above the cue stick is fine for most.Down on the stick may not be indispensable but it affords the best view of the front end of the stick and cue ball and equally important, the eclipse of the object ball; all this while providing the most stable shooting stance there is.
If you can afford this thing then you can afford some lessons. There is probably a whole bunch of other issues as to why your stroke is not straight that this gadget is not addressing. Lessons with a good instructor will fix.The cost is only important to those who can not afford it. If you have an aiming problem, this may help. For those who try this, your feedback may improve the system or even lead to the development of a new product. I like to look at the positive side.
I use a Mason jar and never hit the sides.But is that practical since with most shots, the rail makes the player shoot at a slight angle? That won't work with the bottle exercise. 'Straight' is one thing, but 'level' is different. The bottle requires level as well as straight since the objective is to not hit any of the sides, top or bottom with your cue.
About 20 years ago when this idea came up, someone (Andy something?) suggested using the cover of an old-style small matchbox. That allows some up and down but restricts the side to side. Easy enough to build something like that or just cut it out of cardboard. Adjust the width of the gap to be as tough as wanted. Or just put two golf tees on the table.I use a Mason jar and never hit the sides.