In article ,
"John Harlow" wrote:

I'd like to get input on opinions on the "best" VFR altitude for a route.

It seems to me it's largely based on distance, winds aloft and comfort
level. Do you have a "rule of thumb" trading off altitude (and therefore
safety margin) to avoid headwinds? Or, if winds aloft are to your
advantage, how high would someone go in a 172 class aircraft before returns
diminish?

Some rules of thumb:

A normally aspirated (i.e. no supercharger) engine such as found in a
172 will be running at about 65% power at 7000 density altitude with
wide open throttle. Above that, you will have less power as you climb
higher. Thus, there's usually not a lot of reason to fly much higher
than 7500 MSL, unless terrain forces you higher.

Below 3000 AGL, there tends to be lots of random traffic: people
practicing maneuvers or instrument approaches, and flights entering or
departing traffic patterns. Staying above 3000 AGL keeps you out of the
worst of that. Below 3000, you also run into Class D airspaces, and
there tends to be more turbulence (especially over rough terrain).
Thus, there's usually not a lot of reason to cruise below 3000 AGL.

It's usually not worth spending more than 1/3 of the trip time climbing.

Consider radar and radio coverage. Below 3000 AGL, both tend to be
spotty if you're not within about 10-20 miles of the charted boundary of
a Class B or C airspace (or TRSA).