I was seeing atmospherics at around 43 miles, but I did most of my searching at a 10 mile view. I only zoomed in further on spots that looked particularly interesting.
However, how large is something that "covers many square miles"? A major metropolitan area "covers many square miles" by most definitions but is easily seen from 900 miles or more and will not be entirely covered by clouds. Like you, I suspect that Carpenter (or the reporter) exaggerated the size, as it's an easy mistake to make. An observer on the beach, at sea level, sees the horizon about three miles away. If you were to ask them how much area their view covers, they would likely say that it was many square miles but in reality, it would only be a few.
If the reported size was wrong (which it likely is), what else was wrong?
Obligatory disclaimer: I just enjoy puzzles. There's nothing on Mindanao that's worth my life. I believe that this is largely an intellectual exercise, as even if we found a treasure there, who could go and get it? Without any skin in the game, I'm not inclined to work too hard on the problem. I'll look into it some more as time allows, but I suspect that whatever gold fields are there may as well be on Mars. That's just not a good area for a variety of reasons.
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