Whether one stores it in the cab and puts it under the hood to thaw or just keeps it under the hood, I think the conditions that the container's sujected to are pretty much the same. I was really thinking about doing this just for the winter, going back to the 4 quart bottles in the cab for the warmer temps.

As for the flying bottle syndrome: not if one makes a secure enough bracket.

I don't think the under-hood environment is as nasty as one might think. After all, your cooling, brake, exhaust, oil, etc. systems are all supposed to be closed. In PerfectWorld, the casual observer stuffed under the hood would notice (besides being darned uncomfortable): air being sucked into the engine, heat, a lot of noise. Also, I'm pretty sure that metal bottles have much less of a tendency to absorb chemicals than plastics.

Some years ago, there were a couple of books out about cooking food on your engine block (while driving). Usually, the food was just wrapped in foil and placed in the appropriate spot for the desired temp (top of the exhaust header, between the air cleaner and intake manifold, whatever).

By the by, I went back the reusablebags.com FAQ (link in previous post) to see what they had to say about freezing a KleenKanteen stainless bottle. They say it's not recommended, but can be done.