[Galin]

I don't think it's one idea or the other. In my opinion Tolkien's solution was to include both Round World and Flat World in his Legendarium, and the different ideas concerning the Sun as well. Well, in as much as we can say anything about "finality" with respect to posthumously published material anyway.

And with respect to author published material, there's an example that goes beyond musing: Tolkien revising a statement about the Sun in The Hobbit (Third Edition). . . which (at least in the sense that it takes out a reference to a time under the stars when the Sun did not yet exist) "agrees" well with my reading of Treebeard's tale in The Lord
of The Rings, in which the Sun exists before the Elves sail West over sea.

By the way, lately, but fairly often, I find it difficult to post here due to a Resource Limit Reached message, or something like that. Hmm. Anyone else?