Ok let me do some digging, and i will try to find distances that we sailed across oceans, and publish them here.
However i can categorically state that on cross ocean voyages that i have been doing for over 30 years i have not seen any deviation between published, calculated and actual sailed (steamed) steamed distance of more than 3%.
While Tom can just say they dont know what the flat earth looks like, it is poor argument, and in now way empirical to say that no one knows! The charts we use are published, and available to all, navigation charts have been used for hundreds of years by millions of navigators, and if there is any minor inaccuracy (such a a navigational buoy being out of place, depths changing due to silting or erosion taking place) there is a system in place to make the corrections known worldwide, to ensure we all know.
Given the above and widely available published distances between sea ports, it would be a start, and at least doing something to further the FES to possibly look at producing a chart.
However the first and primary decision would need to be whether there is a South Pole, or if Antarctica exists! So much reliance is based upon the great ice wall, that if it is not Antarctica, then no one has seen anything resembling it, and a two pole earth cannot fit in with our current RE model with Lattitude and Longitude, Magnetic poles and angles of dip, compasses, and distances, that there would be so much weight of empirical evidence (peoples observations, experiences and use of senses to verify the observations) that a bi polar plane earth would have to be dramatic in its extremes and debunk so much empirical evidence, as well as scientific evidence that it just cannot be rationalised by a normal person.
Using Occam’s razor, the bi polar flat earth cannot possibly stand up to scrutiny. Nearly every thing we know about navigation would be wrong, yet not proved, and Tom himself has said that it is not known, therefore the location of continents, magnetism, lattitude longitude would all be assumed!
So taking the model with least assumptions means we end up with the RE model, and unless Tom, or anyone else is prepared to provide this forum with empirical evidence, (actually having done observations and travelled distances, calculated their position on the earth) the FE bi polar world should be consigned to the “ i dont know, it is just a dream i had” shelf!