Dick,
You are measuring an engine that has been cooled well in the approach glide and subsequent taxi run. There is no way of telling what actual full throttle measurement was unless you use an on-board sample and hold system.
I know most modellers do it that way; that does not make it right. I also know, it is so useless that I see no point in doing it that way.
NACA reports on Whirlwind Radials mention 300F (~150C) as standard on cylinders under full load as safe max temperature. (valve housings in the head at 475F)
Like said, in the Rotax manuals, ~430F (220C) is mentioned as absolute redline using a CHT sensor under the plug. Normal operation is about 355F CHT
Our model airplane air cooled gas engines are no different than the full scale brethern, though the small ones should run slightly cooler because their size allows batter heat management.