Storage Compartments Rusting

[Four Seasons]

The storage compartments under my 2015 Minnie Winnie 31K are rusting like crazy, despite annual Krown Rust Control application. There's no water inside the copartments (yet.) The bins are thin, poorly galvanized sheet steel construction with folded corners seams. I had to resupport the outside edge of the right rear bin to the side skirts with steel slotted angle after only three years. At six years and 72,000 kms (45,000 miles) the bottoms of all the bins are starting to sag - they look like flaky brown pastry! I wish they had used the same heavy-duty plastic like the basement!

i can layer some galvanized sheet and strap it, but I wonder if anyone here has suggestions for better ways to improve these storage compartments?

Thanks!