(Blanche Cohen) wrote in message ...
Rule of thumb for mountain flying is to be *at least* 10% under
the max weight. For my cherokee (that tops out at 2400) that
means absolutely no more than 2160. As a rule, during the summer
I try to keep it under 2100 (thank you, density altitude)

No one will fault you for keeping 10% under gross, but I don't think
that is really necessary. Most runways in the mountains are plenty
long for a 172 or cherokee. If you look up the performance data and
add 20% for pilot and aircraft performance, there will not be many
runways that are shorter. After all, if a runway is too small for a
172, how many other aircraft can really use that runway?