JM2¢:
The marks left from the valve notches have to be safe, both because they're original and because they're above the skirt.
The "delicate" areas will be the part of the unsupported crown (away from the skirt and especially away from the pin bosses) closest to the exhaust valve, the plug, and the center of this area.
These will fail first on detonation, but shouldn't give up from inertia at .161".
