I’ve been experimenting with overlays again, and thought these might be useful. 
The scanlines in these overlays fade into the visible lines instead of just being completely solid. These will all produce perfect 1:1 scanlines when opacity is set to 100%. The first is for 4x vertical scale and the next two are for 5x vertical scale.
overlays = 1
overlay0_overlay = scanlines-fade-1920x1080-4x.png
overlay0_full_screen = true
overlay0_descs = 0
overlays = 1
overlay0_overlay = scanlines-fade-1920x1080-5x-ver1.png
overlay0_full_screen = true
overlay0_descs = 0
overlays = 1
overlay0_overlay = scanlines-fade-1920x1080-5x-ver2.png
overlay0_full_screen = true
overlay0_descs = 0