Got an new toy this past week and for measuring temps it's pretty cool. The Spektrum DX8 has telemetry built in and temp is one of the readings available to see on the transmitter screen. It records the hottest temp reading during the power on session as well as giving an instantaneous temp readout.

Dave, your mixture should be adjusted for optimum fuel burn (combustion efficiency) not engine temp. Engine temps should be corrected through proper cooling air baffling and air exit size etc. A glow engine adjusted rich will run cooler with little to no detrimental effect on engine life. A gasser however will create excess carbon when adjusted excessively rich and that carbon can cause premature wear.