Here you have the photo, showing the frame supporting the bottom of the Basil. I used such frames for other loaded baskets and they have worked well for me. The rear of Basil has crumpled over time, as the backpack rested over it. You can see the cracked mesh in the corners. I rescued the back of the basket by riveting an alu sheet over it - it became stiff enough for any further crumpling problem to disappear.
Interesting. I had a similar problem with a BucaBoot (plastic, not metal) cracking where it projected (about 5 inches) behind the rear rack. My solution was to put a PVC 1x6 board underneath, for support. But it looks like aluminum might work, too.