Since most FEr's are a fan of the zetetic method, I will forego any hypothesis and approach a problem without any assumptions.
Let us examine the transit of Venus in 2012 that I was able to observe myself, as were the hundreds of thousands of people that pointed their telescopes at the sun on June 5. The pattern of visibility was as follows:

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Which can be verified by any astronomers on the very edge of the transit, if you are going to argue that no-one in the "not visible" areas bothered to look.
Please elaborate: Why was this pattern of visibility observed rather than the expected arc that would appear on a Flat Earth?