J heads, compression, and today's crappy gas

Just pay attention to the cranking compression/dynamic.
Much over 170 psi is leaving the ease of tune.. for touchy tune and by varying weather pressure conditions ever changing.
I've run 188 psi with a step head quench piston.
165-170 on open iron with flat top pistons and 170-185 with closed chamber or quench piston when using open keeping the distance within .035. Could say .040 ..but to argue that is wasting my time.