I disagree!! Just like on the full size, CHT will remain for some time which is why EGT (exhaust gas temp) is the preferable method when adjusting mixture.
While on the subject, i am an Aircraft engineer and used to look after a fleet of 10 full size Top Dressing aircraft for an operator. His policy was to leave the Engine at a full rich setting for exactly the same reasons under discussion.His quote was "fuel is cheaper than engine overhaul" In 7 years i did not change a single cylinder on any of his aircraft, they did not suffer heat stress because of the cooling provided by a rich setting to all cylinders, even the rear ones. My OPINION,,leave the engine STANDARD and don't look for RPMs or even cyl temps and follow the advice as given by Jeff above.