The unload amount depends on the engine size and its rpm range. If it's a .40 peaking at 14000 on ground, it can probably unload 1000. If it's 1.60 peaking at 9000 on ground, it will unload at most 300~400. I cannot hear that much difference in pitch on my 1.60 in the air at full throttle. Doppler's effect will throw off my sense of pitch.