I've never taken head temperatures, but have always ensured that I have proper duct work that forces the air through the cylinder fins. I look at how the engine is running in the air, and read the sparkplug color and exhaust outlet "sootiness" to determine how the mixture is doing, and leave it at that. As long as you have proper airflow over the fins, use a good quality oil that helps reduce temperatures (such as Amsoil 100:1 synthetic, which I strongly recommend and sign the praises of), and don't experience leaning out of the mixture, it's kind of hard to overheat one of these engines unless you really try to do it by severly overpropping them or doing extended torque rolls and hogh-power/low airflow maneuvers on hot, humid days.

A lot of people are buying the Radioshack infrared temp gun to check their temperatures. You have to get fairly close to the engine, but it's a pretty accurate piece from all accounts. Spots I'd check would be the exhaust port flange, opposite side from the exhaust, cylinder top next tot he sparkplug, and crankcase. Make a chart of these locations for EACH cylinder, taken on a cool day, and then do comparative readings to see what is going on. The crankcase should be substantialy cooler than the cylinder readings, with the hottest spots being the the exhaust area first, plug area second, and top of the motor third, this due to where the intake, power, and exhaust occur on the engine and the related heat of these areas.