Now the outside is fixed I will work on rustprevention from the inside.
I've got a high quality liquid rubber that will be applied on the inside panel overlaps and welds. Then all this will be covered with regular body undercoating.

The car has gained a lot of structural strength again.
Before the rustrepairs, whenever I say, parallel parked on a crowned road, I could hear the car's rear body structure work.

But also when just driving around everything feels way more solid. I've even adjusted the rear shock absorbers one click looser.