Manual Overlay Top&Bottom

safe = Crop(0, 2, 0, -2) 
ConvertToYV24()
 
base1 = Crop(0, 2, 0, 0)
t1 = Crop(0, 0, 0, 1 - Height()).Tweak(cont=1.98)
t2 = Crop(0, 1, 0, 2 - Height()).Tweak(cont=0.95)

StackVertical(t1, t2, base1)

base2 = Crop(0, 0, 0, -2)
b1 = Crop(0, Height() - 1, 0, 0).Tweak(cont=1.07)
b2 = Crop(0, Height() - 2, 0, -1).Tweak(cont=0.99)

StackVertical(base2, b2, b1)
ConvertToYV12()
Overlay(last, safe, x=0, y=2)

• You can play by tweaking contrast values to fix dirty lines (1 is default. Going bellow make the line darker, going over make the line lighter).
• You can add fixes for many lines you want, here is just an example for 2 pixels top and bottom.
• This didn't fix completly black lines, so please doesn't consider as a replacement for FillMargins.