Wow thanks for the quick reply pizaaplanet. I have emailed Iris Taylor (
http://www.itaylorresearch.com/fes_images.html) who I found online to see if she has any other insight or primary sources.
From what you are saying, regardless whether Brimstone Head is a 'corner', the FES has never believed in the earth having corners anyway. I did find online the other corners are the Bermuda Triangle, Hydra and Papua New Guinea. Where do you think this is coming from? None of these seem to have any relationship that I can see.
Also - in regards to the Colombo paragraph. Doesn't the FES believe the North Pole is the centre of the world? If so his sentence doesn't make sense that one can see the edge of the world from the North Pole (or indeed Fogo which is fairly far north).