The crown of the piston is always 1050-1100 degrees, boosted or NA.
Mr. Davis what is your thoughts on JB weld ontop of a piston. How really is it?
Since we have a documented case of it working, I'd try it with a good measure of confidence. It's the same theory behond why EGTs are hotter than the melting point of the head/piston with no ill effects - there's enough engine/mass to help thermally transfer excess heat away from the "hotspots" so bad shit doesn't happen.
I'd use the 1000 degree stuff ktown posted up, though, if it were my labor.