Jabawoky
Are we getting a little miffed ?
What you say is no doubt true in most cases however in this case your answers have little practical application as the overriding limitation to power out put on the DR400-180R is the ease at which the 2700 RPM limit is reached.
It matters not how much theory you apply you can't get past the fact that at anything above 3000 ft and 75 KTS TAS it is just not posable to get 100% power out of the engine and 75% power will be limited by the RPM limit IRO 85kt TAS, all because of the super fine prop. Other DR400-180 variants with cruise props are more than happy to make 75% power up to 8000ft ISA with TAS IRO of 135 Kts at that point they too hit the 2700RPM limit.