As I remember from the Polish guy youtube video, they made the new hinge support from the old one, which was cut out to make room.
Checked that now, and yes, he shows it on the 3rd video, starting at around 1:00. The right hand side hinge support has an L-shape, it also will support the power steering fluid reservoir (red arrow) and also the plastic cover on the bottom of the windshield (blue arrow). The hinge holes are marked with the black dot in the square:
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Starting at 3:00 + 5h15 he shows also the fender support, which was missing in the x250, but is required for headlight stability:
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Around 3:55 he's explaining how he needed to cut a piece of the steel to make room for the hinge support + fender mount. He's showing it only with his finger, so I drove a hypotethical dotted line more or less in the same place:
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Around 4:30 he's showing from the cab the place which can be problematic during welding, as there's butyl insulation on this element.
At 5:40 he's showing the welded and painted elements:
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Another hole is missing in the support, to mount the power steering fluid reservoir. He also tells he welded two nuts for the hinge bolts.
Nothing on the left hand side hinge support though in this video