The crater model would force us to use an equidistance map, like the one they try to use for the 'flat earth'. I struggled with this naturally, but then I installed a massive magnifying glass overhead in my test model, and some interesting things showed up.

Imagine then if our sky, or what may be described as a 'firmament' was formed into the shape of a magnifying lens. This would distort our view of the sun and its motion across the sky. The bending of light around the edges would be extreme, and would add to the illusion of a 'setting' sun.

Considering its size, this lens could potentially or theoretically bend spacetime as well, so that a trip from Sydney AU to the tip of Africa would only take about 12 hours at normal flight speeds, and even the pilot wouldn't notice the difference.

I still don't know how the light of the sun is confined to only half of the surface, but again we can presume that gravitational forces have somehow 'bent' the light as part of the illusion. (is the sun really in the spot we think we see it, or is gravity bending the light and distorting our view? Maybe the sun is not really as overhead as we thought.;)

This vast lens could also account for the seasons, as the 'hot' focused parts would shift on the surface according to yearly discrepancies in the sun's orbit.

This lens might even help the moon's "disc" to appear as an orb as it moves across the sky (otherwise the circular shape of the flat disc would seem to flatten out as the moon moved toward the 'edge' of the lens.)

The magnifying glass sky would then solve some of the problems with the flat earth model that the crater idea forces us to incorporate.

There remains the problem of 'moon phases', and I've come up with nothing to account for a crescent moon when the thing is just a flat disc. My big magnifying lens doesn't help with this issue. Now, if the moon was a spherical object, it would work just fine. Maybe the moon is a holograph, but then I want to know who the hell is projecting the image into the sky, and why.

So, giant magnifying lens, spacetime distortions around the edges, and we have the general illusion. Have fun with this world, and I look forward to the upcoming adventures there (or 'here').