>>11622346What you need is one of those specialized chopping boards, like a NorthWestShortLine Chopper, which is basically a miniature guillotine that allows you to make measured cuts for mass producing small custom-cut pieces.
Also, using my Tamiya Panther Ausf. A for reference which used an Eduard PE kit for the schurzen, you'll want to remember the holes the panels fit onto are larger than the mounting ledges so they can actually slide on. You'll probably be best off just using black flat paint if you don't want to cut these out yourself.