Ferrydude
The fact that the first post specified "low 70s" as an example of the reduced cylinder pressure does not make any reference to compression checkes and does not restrict the question to the subject of compression checks.
I have already agreed that compression checks are unlikely to provide an accurate indication of power output.
Now if you would like to look beyond the validity of compression checks, to consider the effects of reduced cylinder pressures in a running engine, we can move the debate forward.
If you would like to use the IHP equation to demonstrate that reducing cylinder pressure will not reduce IHP and hence BHP, I would be delighted to learn something new.
But further argument about compression checks would be quite futile.