1. You get 80° only on very high altitude and only with rads fully open, but not with 1.2 ata and 2300 revs. lower pressure to 0.9 to 1.0 ata and temps will lower. But 90° are actually not a concern, it gets tricky above a 100°
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2. During a dive, i constantly lower the proppitch, trying to keep the revs at 2200-2300 revs, when pp on 8:30, i use throttle to keep the revs there and finally throttle out. is this correct, probably not
. Same rules do apply to a descent, depending on what is it you want to achieve.