ORIGINAL: Ed Cregger
Actually, it depends upon how the two-stroke engine is timed/ported as to how well it will handle partial throttle operation. Such factors as crankcase stuffing, lower piston fit to the liner, compression ratio, the amount of nitromethane being used in the fuel, glow plug heat range, etc., all play a significant role in tractability.
Smaller throat carbs keep the gas velocity high, which aids in atomization, hence keeping the fire lit. This is particularly important at partial throttle settings, especially when used with larger, higher mass, propellers, as in 3D applications.
The superior exhaust scavenging of a four-stroke engine aids in the four-stroke's ability to recover from a partial throttle setting and return to high speed operation with increased reliability (less hesitation/stumbling). Four-strokes are clearly superior to two-strokes for 3D flying because of this trait. This is especially so when higher percentages of nitromethane are used in the fuel.
This is correct, Ed.
A radically timed engine will be somewhere between 'very hard to tune' and 'impossible'...
However, in a moderately timed engine, intended for mid-high performance level, the carburettor's fuel curve will make all the difference in the world.
With the suitable carburettor (#3219/R from MVVS, which sadly, is no longer made), I managed to make Rossi .45/.53 engines' part throttle behavior, good enough for 3-D flying.