Dumb VTA Question

I might add my tuppence here.
Firstly, Adjusting SRA/VTA makes a huge difference to tracking force on most arms. What you hear is the alteration in tracking force predominantly, unless you reset this after each adjustment....which defeats the purpose of VTA on the fly. Just try it out.
Second point is that to make a substantial difference to SRA you will need to change the base of the tonearm some 10mm to achieve 1 degree change in SRA (depending on the length of the tone arm, 15mm on a 12 inch).
My final point is I took a lot of brilliant photos of my stylus on the record, and measured the SRA repeatedly. I did it so often, I damaged the suspension, and required a cartridge rebuild.....and never managed to achieve 92 degrees. So now I set tone arm level, play around a bit from there, until it sounds right, compensating for tracking force with each change, finally I reset overhang, and alignment.
As illustration, just putting my record weight on my ClearAudio CMB, increases the tracking force by 0.02 grams (it compresses the magnetic bearing and lowers the whole platter), so I can see how a thinner record will see a greater tracking force than a thicker record, the change in SRA will be much < 0.1 degrees. Since not all records are cut at precisely 92 degrees, I'm not sure that this is the holy grail.
I'm sure the debate will go on but after much trouble, I have concluded that the changes in tone arm base height relative to the change in SRA are too great to make a meaningful difference in SRA, but what they do do very effectively is change the tracking force. The change in overhang is tiny, just check geometry with different systems Baerwald/Lofgren/Stephenson, and see the differences are not that small, which to me means a range is acceptable?
I must conclude that I am not an "expert" by a long way, but have had a painful and costly experience with this question, and read just about everything I could lay my hands on, and then did some basic trig on the angles.

I thought I read that M. Fremer wrote that with a 9" arm, a 4mm change in height amounts to a 1 degree SRA change. I have a 12" arm and adjust my SRA for different LPs. I move my arm up and down in a 3mm range which amounts to about a 1/2 degree SRA difference. That sounds tiny, but it is audible and worth the effort to me. I don't then also adjust VTF and overhang, though I know they are effected.

I mark my LPs with the best setting height for reference and this does not correspond to the varying record thicknesses. For example, I have lots of LPs that are say 160g and they cover the full 3mm range of best VTA. Same for my 180g LPs.

Dinster, Baerwald is the best compromise for the records I play. I like to stay as close to that as possible. YMMV.

It is not an issue on my Schroder LT. With this linear tracker I can easily dial alignment in by ear.

Apologies Peterayer, you are correct. I redid the calculations and 5.3mm change in base height on a 12 inch arm (304mm), changes the SRA by 1 degree. Sine theta = vertical change in height (opposite)/length of tone arm (hypotenuse). This adjustment will decrease the overhang by 0.046mm, and change the tracking force a variable amount depending on where the centre of gravity of the tone arm is. My SRA was consistently 95-96 degrees, and I suspect the 15mm came from me thinking that is what I would have to do to get the SRA correct....sink the base in to the plinth!!

Dinster, another way to change SRA is by placing a shim between the cartridge and headshell. Placing the shim behind the cartridge screws will have the same effect as lowering the back of the arm. Of course if you have to lower the back of the cartridge so much that it drags on the record then there is something very wrong.

Using a shim is not an ideal solution but it will at least let you hear if achieving 92 degrees with that cart is a good thing or not.

I find it hard to believe your calculations for overhang change are accurate. They don't jive with my experiments. Could your decimal placement be off?