Hi Mike, I'm going to say a few things purely for the sake of reflection. So I'm not trying to state it definitively

That clean spot could also be caused by the cold mixture flowing into that side of the head, and the temperature being too low to form a layer of black carbon.

I don't think that if there is detonation, it is caused by a compression ratio that is too high. I think it is caused by a squish gap that is too large.

I have seen people increase the crankshaft stroke before https://www.youtube.com/watch?v=pxGF8KyH2NQ&t=91s.

I have been thinking about using that method to make the stroke slightly larger so that the compression increases and to make the squish gap smaller, without running into problems with the length of the timing chain.

It  detrimental to hone away the ring that has formed at the top of the cylinder due to wear on the cylinder if you don,t use an oversized piston and hone the cilinder.This creates a larger space above the piston rings. This not only lowers compression, but also allows liquid gasoline to accumulate, potentially causing vapor blasting and other phenomena that are difficult to foresee or interpret.

It is actually beneficial to make the space between the piston and the cylinder above the piston rings as small as possible.

I wouldn't say that no detonation occurred, judging by the sandblasted appearance. But I would like to rule it out(ore rule it in) out by mounting a detonation sensor.

I know from experience that you are going to ask me questions, but I think I already know that I won't know the answer due to my limited knowledge of 4-stroke tuning.
I am afraid that my ignorance about this will become apparent, so I want to preempt that.