I have A 1964 Mercedes SL pagoda and I made fender liners for it out of sheet metal because I removed A bucket full of dirt from inside the chassis and corners of the body. there is a hole in the chassis that defines the crumple zone, where all the dirt goes inside the chassis and starts rust from the inside. since I installed the liners there is no such problem. they are half liners actually. they only cover the back side of the wheel arc.
but looking at the pictures in this post I would definitely put the l brackets behind the liner, that would make a better looking finish and also protect the screws that go through the body more. those screw holes might be a new point where corrosion starts