CMC vs cab mount relocation, also homemade fender liners?

That is very good to hear that the Kydex actually works well for this, and sounds like you did basically exactly what I was thinking in terms of securing and shaping it. I've made some things in the past using it (although working with much smaller pieces than would be for fender liners) and it seems like the perfect material for the job. Had also considered making new, slimmer mud flaps using it, it actually appears to be what Rokblokz uses for their $150 flaps (just going on the photos Ive seen of them)

 

So I didn’t do the single piece ones like that but very similar. My biggest tip is make the holes in the kydex larger than you need so you have some wiggle room.

 

That looks super clean, nice work