cutting stylus angle: Microgroove vs 78 standard

[Steve E.]

A kind soul here sent me a steel audiopoint cutting stylus in the old 78 "Standard gauge."

I took a couple of very unscientific pictures of it using the camera in my phone.

In this picture, it is the center stylus. An Apollo 362 short shank is on the right.

angle-compare.jpg

Here is the stylus from the side:

side-angle.jpg

What do the experts say? Am I correct on these angles?

I've been told that the angle doesn't matter so much if I am trying to get a decent cut playable on a 78 machine: That it is the width that matters. The one advantage I can see to a 100 degree cut is that it would allow a wider groove without having to cut as deep into the acetate. This, by extension, potentially reduces the risk of cutting into the aluminum (is that a real danger?) and doesn't demand as much scooping out of material, which would stress the whole system less. Are these real concerns? Experts?

[Steve E.]

bump! to be clear, I am trying to learn all the typical facet angles for 78 "standard" cutting needles of the 1940s.