That piston design never really took off,most hemi pistons are designed to conform to the head and as with any piston the closer to the head chamber the piston comes the better the efficiency of combustion on a cylinder design that is superior with the charge and exhaust inherient to the design.Ignition and flame propagation is centrally located and intake charge is directed to the compression zone as well as the the exhaust is directed to the exit valve location.There is little turbulance encountered in the charge and exhaust.Hemi,semi hemi,and canted valve heads will alway perform better than a straight line valve arrangment.Simply put a piston that conforms to the combustion chamber will alway be more efficient because it has a more uniform area of compression and ignition,a flat piston with a small combustion chamber and a straight line valve arrangment tends to load the piston unevenly,quench helps even the load.