I just came back from a fishing and hiking trip on the Futaleufu in Chile (east of Chaiten).
It was a great trip, although with the time of year we fished lakes more than rivers. We had great action tossing dragonflies and big Adams drys into the weeds. Some of the browns seemed to be as big as my leg.
If you need any info regarding that area then let me know. I might have a good contact for you in Chile.