The new ignitions with onboard recorders really put an end to the speculation -
On most - you can read rpm as you setup the prop and engine - then read the inflight rpm after landing .
This really fills you in on what power you are making -in your flight situation
fo example -if all you do is take off and hover around like a hawk over a mouse - you want the engine revving easily ready to leap in a instant -
If you do a little of everything - prop up a bit more - if you keep cruisin all the time run a prop that allows lower rpm for mor speed - you get the picture .
Example :
for the 3D stuff which really stays at high angles of attck - I prop my engine ( it is not a DA50) for at least 7500 on the ground and over 8000 in the air . ( 22x8 mejzlic)
For quieter performance - add more prop - for quiet really good IMAC-- a prop that is running 6700 on the ground and 7600 in the air . 23x8/ wider thicker 22x8/22x10 etc..
I can't seem to hurt my engines letting em rev - and the setups I use permit that - others setups may not tolerate this -
case -by case.
In air performance is the objective -of course -If your setup satisfies you - objective achieved-
Tho I prop my 50 for numbers noted - -I prop my Evolution 26 - for up to and over 10000-in the air - again- no problems .
It is surprising to find how high, actual in flight numbers are on some setups