I have a mint parcel shelf in my spare mk2, and can easily cut it out. The problem is with welding... To do a good job here, it'll cost quite a lot for this, as I've seen a few with really messed up bulkheads and the bit under the rear screen after welding this.
So I thought: Can I cut out the old one leaving a border of a few cm around, and screw the new one onto the old one with like 50 bolts/nuts? To show what I mean see the attached picture. The red bit is what would be left from the original shelf and the black is the new shelf.