I found this on the aprilia web site. If I could figure how to copy & paste I'd do that. But just took a page of notes & took a pic. Idk if this helps, I know aprilia is a totally different animal, but the fundamentals should be the same or at apply. I would think anyhow.
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9.5:1 is pretty high comp for these china girls so 60% of bore is a bit over kill as this would be done on a much larger bore to maintain correct msv, msv is the speed at which the charge travels toward the flame front as it propagates outward to consume the charge in the combustion area. The squish area is to compress the end gasses in such a confined space that they super cool not being consumed by the combustion and this transfers to the piston's crown (outer edges) area and then prevents detonation or ping from occurring. Squish area as a percentage to the bore Jennings say's 50% of the bore is a general all around starting point but that relies on the head being cut that way which it's not in many cases, he also said this on the topic,
With small-bore engines you may push the compression ratio up to perhaps 6.5:l without
serious consequences, using a non-squish cylinder head, but that is very near the limit.
Good squish-band cylinder heads, on the other hand, permit compression ratios up to as
much as 9.5:l in motocross engines with exhaust systems that provide a wide boost
without any substantial peaks, but for road racing engines I cannot recommend anything
above 8.5:l, even when unit cylinder size is only 125cc. You will find that higher
compression ratios than those suggested can produce marvelously impressive flash
readings on a dynamometer; as soon as the engine has a chance to get up to full
temperature, the output will drop well below that sustained by an otherwise identical
engine with a lower compression ratio. Sustained, and not flash horsepower, is what wins races.
