So I've got at least a few claims here that I want to work out, because I think they're pretty fundamental to both models flat and round.
1 ) We exist in grounded, objective reality.
2 ) The subjective, first-person experience is the only exception to the first claim. Barring that one exception, there is nothing that any one person can observe that another person cannot also observe, congruently, given that both observers repeat the same experiment and possess the same physical capacity to observe (literally sense of sight, hearing, taste, etc.).
3 ) Differences in opinion can be meted out as factual, plausible, or inconclusive.
4 ) With respect to the competing models of the earth, only one model comports with reality - it can't be both.
I think it's important that we agree on these premises if we're ever going to make any headway. It's hard enough getting people to stop yammering on about the conspiracy claims and ignoring simple, cogent explanations, but then every so often some solipsistic tripe makes its way into the conversation.
I don't know if there's anyone here who disagrees strongly enough with these premises to make a counter claim, but I invite anyone to play devil's advocate, if that is indeed the case.
The floor is yours, gentlemen.