That is one of the points (there are others) that I'm not all that sure about. These days you would either have to get some very old POC shafts, or literally have to sort through thousands of shafts these days to find some. Byron is having his source keep an eye out the some of the best that he can find. This could take a long while.

Just wondering if you discredit Howard Hill making the shot in Robinhood? Acrording to him, this was not his most difficult shot.