Just a few comments about the spare-gas-container-in-the-luggage-rack idea. I
had placed a plastic container up there with gasoline (2 gallon Rubbermaid)
and did a quick run to King's Canyon in the Sequoia National Forest near
Fresno. It was a late morning to midday drive and typical California Central
Valley hot. I checked the container just outside Fresno and it was hot, soft
and far more spherical than when I started in LA. I left it there and checked
it again several days later when we were to leave the campground. Still quite
rounded, I checked the volume. It now contained a little less than 1.5
gallons. Haven't put one up there since. I suspect it would be fine if
covered, but when camping all the space up there is used by my luggage bag,
filled with the Westphalia tent, poles, camping chairs and other
miscellaneous.