Map can't load...size problem?

I don't have an answer to this. However you could try ruling out a specific CE build bug by expanding a map to 2048x2048 with the original FF6LE and see if it loads in-game. Maybe just changing a map size won't affect the tilemap and you'll be able to save. Worst case scenario you could trash other maps just for the sake of the test. I don't think that's a specific CE build bug since I have not touched that part of the editor. Maybe the game does not support it, you'd need to look at the game ASM code. Maybe the max supported sizes are 1024x2048 and 2048x1024, I have no idea really..

I could look into it, but first I'll tackle the tilemap bug you reported last week. I haven't had the time yet but I'll do my best to fix it as quickly as possible.