I think if you can find a good UT guy he can measure the depth with ultrasound. Check with Pat McRat he may have an option since he does CMM. Might be able to CMM Ultrasound them and see the profile of the oil passage.
If the valves were not opening and the injector was still firing, I don't think any piston would have survived...kind of impressed it wasn't worse.This was my piston and the story behind it is my rocker shaft snapped in my head doing a WOT pull and after tearing it apart my valves we not opening at all on that cylinder. Not sure how that affected the piston exactly but that was when this occurred.
They probably only had like 25 pulls on them. One of my rocker shaft bolts were pushed up and ripped the threads out of the head and broke the rocker shaft in the head in half so it was no longer bolted down so the valves were not operating at all.That's definitely impressive. How many pulls do you have on those? What caused the valves to stop opening?