Smartstylus accessory to SmarTractor-cantilever angle?


Can someone please explain the concept of a gauge for cantilever angle? http://www.arche-headshell.de/alignment-tools/smartstylus/
It seems obvious that cantilever angle and the relative angle of the stylus on the cantilever are fixed. Any change of the cantilever angle is not going to change the stylus angle, it will only change the SRA relative to the record surface. I also understand that more often than not, the angle of the stylus on the cantilever is not optimum-a parallel armwand to record surface is no guarantee of achieving even approximate optimum SRA. So why even bother aligning with cantilever angle in mind? 
At the risk of answering my own question, I am going to guess that the gauge is meant as a starting point only and then examining SRA but I am not trolling here, I find this puzzling. 
128x128fsonicsmith
fsonicsmith
Can someone please explain the concept of a gauge for cantilever angle? http://www.arche-headshell.de/alignment-tools/smartstylus/
It seems obvious that cantilever angle and the relative angle of the stylus on the cantilever are fixed.
They are fixed in respect to each other, but they are not fixed with respect to the record surface. One of the best ways to set the correct VTA is to measure the actual cantilever angle to the LP, as opposed to trying to get it right by looking only at the height of the pickup arm.

Any change of the cantilever angle is not going to change the stylus angle, it will only change the SRA relative to the record surface.
Changing the angle between the cantilever and the LP surface will change both VTA and SRA.

I also understand that more often than not, the angle of the stylus on the cantilever is not optimum-a parallel armwand to record surface is no guarantee of achieving even approximate optimum SRA. So why even bother aligning with cantilever angle in mind?
Correct - a pickup arm that is parallel to the LP is no assurance of correct VTA. That’s why it makes sense to measure the actual VTA, which measuring the cantilever itself facilitates.
While I can support the method of directly measuring SRA via a USB microscope it is both awkward and in many cases next to impossible if you have a tricky stylus profile. Furthermore limitations in technique make it difficult to get accuracy to more than a couple of degrees.

For these reasons I’ve stopped using this method and instead find the AS SmartStylus a much more practical and simple tool for going directly to VTA.

Or easier still let measurements guide you ... and be certain you’ve gotten to the right answer 😉 if you have the means this approach will give you true peace of mind
https://www.analogmagik.com/vta