I try to give Flat Earth a fair hearing but the Southern Hemisphere is a real problem for it. The extreme distances is just the beginning.
Hervé Riboni, a round the world yachtsman has adressed a number of issues regarding this.
His videos can be found on the Taboo Conspiracy Youtube channel. He argues that the distances in the southern hemisphere are far less than what we have been told and that the magnetic declination and time zones hide the flat earth
Concerning the round the world yacht races, he states that the doldrums in the middle of the Atlantic and the roaring 50s in the southern hemisphere make the journey to the south takes far longer than expected and masks the distance, whilst the speedy winds in the South explains how this race is possible on flat earth.
All his videos are worth watching for their level of detail and technical explanation. He is a genuine yachtsman who has put his reputation on the likne to get this information out. This screenshot is from
https://en.wikipedia.org/wiki/List_of_The_Ocean_Race_sailors