I did not model anything, I am too old for that, and therefore totally intuitive according to what I learned 50 years ago on the decomposition and the transmission of the constraints.
This is for street use, but when I saw the cracks including in the pewter trim in the corners of the engine compartment opening, near the lights, I thought it was all there openness that needed to be strengthened.
200 or 300 pounds ...... I think there is one zero too many; i'm not at home but I will weigh the top brace which is taken apart when I get home, I think it weighs less than 10kg, these are just tubes. The rear cross member is a bit heavier, but it is located very low and that lowers the center of gravity.
I like light cars a lot, I have a 1996 TVR Griffith 500 (1050 kg and 300 HP) and a Westfield replica of Lotus Seven (Collin Chapman said "light is right") (620kg and 190 HP), but they don't have a big all-cast American V8. Just by replacing the original cast iron intake manifold with an aluminum Blue Thunder and the cast iron water pump with an aluminum one, I had to compensate for the weight of the reinforcements.
The anchor points welded to the thin sheet are positioned exactly opposite the reinforcing "side members" located in the wheel arches on the other side of the sheet, the forces will therefore be transmitted to the structure and obviously not to simple plate sheets that have no resistance.