Hi, first-time posting. Just purchased a 2020 Metris 126" cargo van off the lot for our food bank, and I want to add panels to the unprotected openings in the back. I'm going to cut my own out of Coroplast. The lower panels seem easy enough to attach using pretty standard panel clips. But I've learned from other threads that the upper cargo panels don't install using plastic trim clips like the lower ones, but instead use screws into U-clips that attach to the edge of the body panel around the openings. These are part # A004-994-71-45 and apparently available only from Germany, so sometimes take awhile to get on order. Has anyone successfully used non-Mercedes generic U-clips in their place?