I don't know about some of the exotic woods, but I sure wouldn't use red cedar considering it's prime characteristic is how easily it splits as well as how easily it dents - good yellow cedar might work, but wouldn't be on the top of the list of possibilities either
don't know enuff about Araucaria as lumber, but what I've seen is pretty knotty w/ interesting grain that might not lend itself to long term stability as planks - if you have access to some straight grain away from heartwood, you could try some testing for weathering, stability, and durability - otherwise there's lotsa fir around!
Bill
