Change Header Image Size When Cropping

Hi all,

I’m having an issue with my header image in a twenty sixteen child theme. I have changed the size to 1320x312px, but I seem to be missing something. “.header-image” does display properly, however, when zoomed out, the header image is still 1200x280px and does not fill the container. Also, when uploading a new image, it will still crop to 1200x280px.
What I have done so far in my child themes files:
Changed CSS (works fine. I could force “.header-image img” width to 100%, however, that would pixelate the 1200px image, so it’s no option).
Changed Banner Resolution in inc/customizer.php
Added theme support for custom headers in functions.php: add_theme_support( ‘custom-header’, array( […] and also tried add_filter( ‘twentysixteen_custom_header_args’, ‘wpb_new_header_size’); […]
Well, so far nothing worked and I’m stuck – I found fixes for other themes when searching, but they weren’t applicable. So here’s my question: What am my missing to make the header image crop to 1320x312px?

Thank you all in advance 🙂

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