Hole in piston

[Bob Culver]

The plot thickens. Still difficult to know what started generation of all the heat in the first place. Possibly a part seizure which has persisted long enough generate a lot of heat and  to overload the big end.  I wonder if the engine had been recently rebuilt tight or piston walls built out with corrosion? Is the piston the less foregiving solid skirt type? 
Whether the big end or piston seized first, the conrod has had a severe working.
Not relevant, but are the top rings different thickness'?