Protect engine compartment against martens

Good evening, I’m not sure if this is the right area for my question. Wouldn’t like to protect my vehicle against martens that are very active now in spring. Since my vehicle has a rather small underrun protection. (See photos) And since I’ve had a marten bite several times, I guess the colleagues climb in there. My idea is to close the way as shown with the boxes (see photos), with a plastic cover and metal screws. would be: What about the engine temperature? (Would the plastic pieces still have holes in the diameter of ca-3.4cm. Metal screws in the axle carrier? Would this be a problem from the stability? High-voltage plates in addition to the wheel houses, or longitudinal beams (where they also come in) Greetings