Thanks!
At your game resolution, default-height levels show only 85 % of vertical height, potentially hiding important ledges.
I don't yet know what to do. The zoom is 2 (every physics pixel generates a 2x2 block on the screen). Zoom 1 is too small, default-sized levels would fill only 30 % of the area. I haven't tested yet whether non-integer zoom looks good at all, I believe it won't look any good. I'd rather not make the levels smaller, a good solution shouldn't depend on level size.
-- Simon