Tricky to fit and can't be rushed....some pictures of the front arches to compare with yours.....One hole gets filled in after being flattened.....rear lower.
I like to have a lip for added strength so you can see here where I trim back to.
at the front and rear edges of the plastic arch some trimming is required.......at the edge which meets the sill you'll need some boiling water to heat the plastic for the final fit.