If I want to prove something and there are 20 points to consider, I don't want to just talk about one point.
For that one point might be weak, thereby making the whole argument weak. And likewise, might be strong, covering up for other weaker points.
Don't confuse talking about a variety of points with moving the goal posts. And you don't decide that point(s), we do.
Feel free not to take part.
The thing you are skipping with the flat earth model is that we don't know where the sun really is. Many now feel we are seeing a reflection
of the sun and that it really exists outside the firmament. This is the most difficult part of the flat Earth hypotheses imo.
Re the radius of the circle, note, the radius of the Earth was determined by around the time they were guessing the distance of the sun and
around the time they were using Venus passing in front of it to do so. If the radius of the Earth is what they say it is, then we should NOT
be seeing as far as we do (with high powered cameras and telescopes.)
Many (old) flat Earth maps show Antartica on the periphery and further they show more lands beyond that periphery. Which interestingly
enough is what Admiral Byrd said in his interview on TV. (Not to mention the vast coal reserves that would solve our energy problems.)
Re your "calling your friend and seeing if it is light there" type of thinking. I like that and it has been done. I know Globebusters were
talking about this very thing and getting into the details. I just forget the episode. Was in the last 4 months or so.
Related and more accessible now, is the falsified video coming from Antartica. They show constant light, but by looking at the shadows
of the objects in the film, you can see they looped the video and cut out a huge part. https://www.youtube.com/watch?v=7Mdg5k-WBFw
At some point, from long distance photography, to ISS green/blue screen mistakes, to the Antartica lies, the Globe Model breaks down.