Edwin
Yes, when I finished installing the finders, basket, etc, I decided there was still a chance for upspray from my tire onto the underside of my basket cargo and also onto the front dynamo headlamp.
I've used heavy plastic film for a couple DIY projects and I have a stack of that material. I've acquired this heavy plastic film in three ways:
1. I bought a sheet at TAP plastics
2. I've deconstructed file folder products from the Office Supply store (generally upcycled items discarded at my office)
3. The Elfa brand shelving that I've run in several closets in my home came with plastic shelf liners. I've decided not to line every shelf I installed, but kept the extras for future projects
I took one sheet of my stockpile material and made a little rack topper. This augments the fender and protects everything that is on top of the rack from spray. Here's another photo of that
SPLASHGUARD with a caption describing it.