I moved the mudflap I’d made from an old shoe tongue (green leather PF Flyers Hi-Tops, to be precise) from the inside of the fender to the outside. I used the same double eyebolts I’d used on the inside, and cut the flaps down to the wide part.
The flaps on the inside would catch the tire on bumps, and get sucked up inside the fender. Partly it was the size of the tire, and the vestigial knobs (they’re IRC Mythos CX Slicks, and I cut the side knobs off with scissors), but mostly the problem was that when the flap was swept back by the rushing wind of my incredible speed (about 4 knots), folded origami-style, and poked a ridge straight at the tire. Fold a paper cup in half, and you’ll see a similar ridge.
I used a hole punch to punch the holes, which worked a lot better than the awl on my Swiss Army knife.