The Roof Line

There was a lap in the inner skin of the door frame, just behind the B-post, which matched with a similar lap joint in the Variant. I unzipped the front portions of the inner skin so that it would join again at this lap.
The lap joint can be seen behind the B-post inside the car, immediately in front (to the left) of the interior light bracket. This is the right-hand side of the car.

Here is the rear of the frame prior to welding.

And the top of the B-post seen from the outside.

I clamped the top to squeeze the gap tight before welding everything together.