Head Gasket,Cracked head or hole in piston

Hi Benton,
After looking at the pictures, I'm not totally convinced preignition
was the total cause of the piston failure.
The edges of the breakage is too sharp, preignition usually pits and
melts things a bit before failure like in the the 2nd picture.
I'm wondering if maybe ring end gap and a lean condition then detonation may have
combined to cause the problem at high rpm.
At what rpm did you notice the rattle or ping during last years racing?