Making terrain follow the grid in world editor

[$HAZM]

Hey, I'm trying to use terrain for pathability. the problem is my whole map is built within the grid in world editor, and the terrain tool is painting the terrain half in one square of the grid, half in the next, and it's messing everything up. Is there a way to make either smaller terrain tiles, bigger terrain tiles, or make the terrain follow the gird? I think i saw something about alpha tiles that follow the gird, so it must be possible? Thank you