Looks like a great trip, Neil!
20 good sized trout per day sounds pretty good to me. I'm putting the Yelcho on my BL as so today!
When we fished the Petrohue, it was the same for us with flies; mostly locally tied streamers, 6 wts. and heavier leaders/tippet. We had to hike up into some of the tribs, like the San Antonio, to use the kind of gear (3 wts. and 4 wts., 5x tippet, mayfly dries, etc.) that we would normally use here in the East on the freestone/limestone streams.
The Andes are just something that you have to see to believe. With their steep faces, jagged snow-covered peaks and glaciers, they make even the Alps look like old mountains.
And the food........and the wine............and the friendly people.........
It's also an area of climatic extremes. for example, I was skiing at Portillo one day and a week later we were fly fishing in Northern Patagonia.
I'm thinking seriously about going way down next time; below Balmaceda, into the Torres del Paine national park area. The fly fishing reports that I get from people who have been there are hard to believe...........which, of course, means that you have to go and check it out for yourself.....just to be sure.
Thanks for sharing this great trip.