Something that a lot of pilots don't seem to realize is that if you're flying up at '75% altitude' (7500-8500 feet msl, depending on who you ask and the phase of the moon), you don't get 75% power unless you're turning at the rated full power rpm and full throttle.
Yes, this is a rough number (and only applies to normally aspirated engines), but it's pretty close to reality. Most (including me) are happy to fly at less than 2700 rpm, but we shouldn't kid ourselves that we're getting 75% power while doing it (unless we're at a significantly lower, less efficient altitude).
Charlie