Hi Richard,
You might find this thread useful, https://www.whatsbestforum.com/threa...ception.35324/
Note that table in post #2 in the thread as below, where s is the increase in height of the tonearm and ?2 is the resulting angle of SRA (assuming the stylus is correctly mounted in the first place.
s (mm) ?2 (deg)
0.1 21.2
0.2 22.5
0.3 23.7
Conclusion: fraction of mm results in significant change in SRA. Note: slight over estimates
I have not checked the maths.
I believe the best method is to start with the head shell parallel to the record surface and then adjust the tonearm up or down a little at a time to get the best SQ.