I agree, 230° is pretty hot for most street builds, and I think most builders would be happy with that as a limit - especially if it speeds up the piston process and reduces the price.
I have a nagging thought that may just be my bad memory playing tricks - do hypereutectic pistons have a "skin" of higher Rockwell at the external surfaces? This phenomenon is, IMHO, not yet well understood as a physical property (how extra surface area improves the strength of some objects), but my concern is if it's safe to machine reliefs afterward if needed?
Since the alloy is a bit brittle (vs. the usual casting and forging material) any cut at all should be done slowly, proper lubricant (I'd ask John Erb, even though he's retired from KB he's still around somewhere), have a generous radius, and blended in to the remaining casting for safety.
If this is a "yes" KB may be happier to accept this commission because it gives them 2 steps forward on 307 and Sprint (which I think has reliefs) pistons - always nice to use OPM to develop your own products!
