"Filtering->Crop/Resize->Base->Letterbox", is the only way Hybrid support letterboxing.
Hybrid doesn't support custom border definitions like 'add 3 left, 2 top, 1 bottom, 3 right'.
So what you want is not possible in Hybrid atm.
Instead of adding 42pixels on the left and 38 pixels on the right, Hybrid atm. only supports adding 40 pixels on each side through letterbox.
Cu Selur
Hybrid doesn't support custom border definitions like 'add 3 left, 2 top, 1 bottom, 3 right'.
So what you want is not possible in Hybrid atm.

Instead of adding 42pixels on the left and 38 pixels on the right, Hybrid atm. only supports adding 40 pixels on each side through letterbox.
Cu Selur
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Dev versions are in the 'experimental'-folder of my GoogleDrive, which is linked on the download page.
Dev versions are in the 'experimental'-folder of my GoogleDrive, which is linked on the download page.