FFF
There is nothing wrong with a cruise climb power setting, right after takeoff, terrain permitting - except that the airflow around the engine won't be what it is at level cruise and I would think many/most engines would eventually overheat if you did it at say Vx. And do you have a CHT gauge, and a working one?
I've never seen a working one in any of at least a dozen hire planes. Now I have an EDM700 which is very interesting to watch in different situations.
If the POH says something is OK, then it should be OK. The danger is in using rules like 25/2500 generally.
SAS
I agree re the power settings without a flowmeter - provided you apply the correct altitude compensation to the MP value, about 0.5" to 1" extra (or so) per 1000ft - this is because the fuel metering (or a carb) doesn't measure mass flow; it measures air by something between volume flow and mass flow, whereas it measures the fuel by mass only. But few spamcans fly high enough for this to matter.