That wouldn’t solve the problem of misplaced/weird scanlines when using an overlay that has a different Y than the Y of the custom ratio, though. The goal is to have one overlay per scanline pattern for the the 3x patterns, 4x patterns and 5x patterns. This cuts down the number of overlays from 30 something to 16.
No, there’s no way to tile anything, but that would probably be fairly easy to add…
I think it would be worth it to add this function, for the above reason that you can then create a single scanline overlay with a 3x, 4x, or 5x pattern and then get it to work with any 3x, 4x, or 5x resolution (respectively). I think that’s probably the easiest way to cut down on the number of overlays.