That's a good point. The long and short of it is.....so far i've done nothing.
Right from the beginning I had intended to make a trim piece that masked the gap, but because the bike functions fine without any covering I lowered my priority for making something.
The reason why it's still not been done is mainly that I couldn't make my mind up as to how to do it.
For example, I could do a 3d printed trim, but it would be tricky to fix and be robust. It might take a few trys to get something that I both like and stays put when the going gets rough, so to say.
I could make something out of thin stainless sheet, but i'd have to make a 90degree bend in it and overlap the sides of the rack and fix it with self-tapping screws, but to do a complete job of it, i'd need to do it on both sides of the rack frame so that's x4 pieces.
So apathy set in over time and I got used to how it looks......well.....kinda. I would still like to do something aesthetically nice.
It doesn't matter about water getting in, as it just drains away anyway, so it's purely aesthetic requirement/preference.
One thing that I would like to do when I have time, is to make a side feature that enables a more versatile hooking function for straps/bungees etc...
I'm therefore thinking that I could make something that does both things in one part. That makes more of an incentive to make something.
Might do something next winter, but not now.....now it's time to ride.