Based on the handy 'map' you posted (why arent all the lines parallel?), sailing the coast of Antarctica one would expect to travel about 2.4 times the distance compared to sailing the coast of Africa. Now all I need is a ship and supplies for about 5 years.

Flat Earth is simple well poisoning. I did manage to find a flat earther to debate once, but they fled the debate when I pointed out they were using the opposite claim in one argument that they relied upon in an earlier argument. I enjoyed it, it is often a challenge to spot the hidden erroneous assumptions they use.

Flat earthers make claims, usually based on a frame-of-reference error, but they never debunk the proofs for globe earth. I put it to this one flat earther "how is it that I can call a friend in Australia and it is daytime there but night time where I am" this led to the claim that light gradually slows down and eventually stops. I guess the sun is there at night but just too far away?

It is just very difficult to find a flat earther that understands flat earth enough to explain it, I have not met one.