All Tigers had two openings in their rear mudflaps. One opening was larger than the other one. In the "early" version of Tiger, as represented by this kit, the larger opening had a complex shape that you can see here.
Ustar have given us mudflaps with two simple rectangular openings. To reproduce the complex shape you must cut away a little plastic, which is pre-thinned for you.
But there is a mistake in Ustar's part. A real Tiger always had the larger opening on the left side, but Ustar have "mirrored" the part and one of them is wrong. You could perhaps fix it by moving the central barrier that I indicate on the photo.
The openings are not the only problem in Ustar's parts. The real mudflap was a flat sheet of metal with stiffeners welded on top and no side wall. There was a slight fold at its lower edge (arrowed here).
Ustar have given their part a much wider end wall, and a side wall (white arrow) that it should not have. It's not a sheet but a tub.