I have a cheaper experiment which I posted on Eric Dubay's videos and facebook page (I did not realize he is a controversial figure) but here is my experiment as addressed to Mr. Dubay:

I wonder if we could start a crowd funding campaign to buy Eric Dubay a series of plane tickets that would allow him to fly around the world in one easterly direction without ever leaving the southern hemisphere in a fraction of the time that any map of a flat earth would indicate was possible. Here are some flights and flight times taken from Kayak.com that would do the trick:
3:55p — 6:40p
Economy 2h 45m
Buenos Aires (EZE) — São Paulo (GRU)
GOL Linhas Aéreas 7453  ·  Narrow-body jet  ·  Boeing 737-800
Change planes in São Paulo (GRU)  Long layover
4h 55m
11:35p — 1:00p
Lands Sat, Apr 1
Economy 8h 25m
São Paulo (GRU) — Johannesburg (JNB)
South African 225  ·  Wide-body jet  ·  Airbus A330-200

7:10p — 3:55p
Lands Sat, Apr 1
Economy 11h 45m
Johannesburg (JNB) — Sydney (SYD) 2 seats remain
Qantas Airways 64  ·  Wide-body jet  ·  Boeing 747-400

16h 00m
1:50p — 6:55p
Economy 3h 05m
Sydney (SYD) — Auckland (AKL)
Air New Zealand 710  ·  Narrow-body jet  ·  Airbus A320-100/200
Change planes in Auckland (AKL) 
1h 10m
8:05p — 3:50p
Prem 11h 45m
Auckland (AKL) — Buenos Aires (EZE)
Air New Zealand 30  ·  Wide-body jet  ·  Boeing 787-9

Total time in the air is 37 hours and 45 minutes (not counting layovers). With an average speed in the air of say 580 mph (which is very generous given the aircraft being used), this would mean a maximum total distance of 21,895 miles to circumnavigate the globe while staying within the Souuthern Hemisphere. Note that these flights actually includes some north and south deviation which will add distance and time in the air which means this figure is higher than would be absolutely necessary to circumnavigate, but again all of these flights stay entirely within the Southern Hemisphere and so do not cross the equator.

Since both flat earthers and globe earthers agree that the distance around the equator is more than 24,000 miles (flat earth models actually have the distance around the equator as 39,000 miles-see note below), then it should not be possible to circumnavigate the globe within the southern hemisphere while only being in the air for 37 hours and 45 minutes while using modern day commercial aricraft. And it should be even more impossible with a flat earth model where the distance at the southern latitudes of the cities traversed would be much, much greater. Sao Paulo is the northernmost city on this itinerary and is 7991 miles from the North Pole. So the circumference of the earth at that latitude on a flat earth would be over 50, 200 miles.

The question I would pose to Mr. Dubay is "If you personally traveled around the world in a combined flight time of less than 38 hours without leaving the Southern Hemisphere, would you then be willing to admit that the flat earth model you propose is fatally flawed?" If the answer is yes, then maybe we could get a crowd-funding project to buy your tickets and put this whole debate to rest. What do you say, Mr Dubay? Are you willing to test your theory in a real world experiment that cannot be faked and that would allow you to time your own flights, and use whatever means you need to use to determine that you were truly in the cities included on this circumnavigation trip and had stayed within the Southern Hemisphere?

Note regarding the distance around the equator: I found this post on the following page:https://www.theflatearthsociety.org/forum/index.php?topic=59426.0

"A thought occured to me when doing the maths for my ladder experiment: the distance around the equator is drastically different between FE and RE models. Both models use the same equation: C = t*r, but each have a different radius. For RE, the radius is that of the Earth at 6371 km (3,959 mi); for FE it's the distance from the north pole to the equator, roughly 10,009 km (6219 mi).

Thus, RE says the equator is roughly 40,000 km (24,874 mi) while FE says it should be 62,888 km (39,077 mi). In 1986 an historical and well-documented flight took place wherein two people got into an airplane at Edwards Air Force Base and took off. Just over nine days later they landed at Edwards Air Force Base, having circled the Earth more or less about the Equator[1][2] with a total flight distance of 40,212 kilometers (24,987 miles).

Was this a scam? Did the pilots fly a shorter, northern route for nine days instead of sticking to the equator? Or is the FE distance around the equator false?"

It is from these calculations that I came up with the 39,000 mile length of the equator for the flat earth, and then extrpolated based on the distance to Sao Paulo from the North Pole.

Who knows, we might even get some flat earth people to go along and test it with Mr. Dubay. The total cost for the around the world portion of the journey would be under $5000 (there is a cheaper flight from Sydney to Buenos Aries through Santiago). Are there any true believers in the flat earth that would be willing to put their beliefs on the line for $5000? Or are there enough people who are just tired of the arguments back and forth that would be willing to pay for Mr. Dubay to make the trip and settle this question once and for all? I would chip in $100 to such a crowd-funding effort.

The ball is in your court, Mr. Dubay. Are you game to test your own theory?

Note added: Anyone on this website willing to make the journey? At just $5-7000, it would seem like a quick and easy way for the believers in a flat earth to test their theory.