Blue, like John stated, roll cage loading could come from any direction, so it's much more difficult to optimize than a bicycle. On a bike, there are only a few load paths. You have the rider's weight on the pedals and/or seat and bars, and loads going through the tires from various angles. In a race car, you could be hit from any direction and in infinite concentrations. If stiffness was the ONLY concern, it would be simple to model. If you are just looking at front end stiffness, yes, that could easily be modeled. Again though, it depends if you are building to a rulebook or just for personal use. Some sanctioning bodies allow the cage to be tied into the chassis and others don't. You also have ease of service to consider. In your options above, "A" sucks for stiffness, but it's the only one that can be swung out of the way to remove the valve cover. "B" requires very little modification to the car, while "C" connects to the rails, requiring more extensive mods. The car in picture "D" doesn't use the OE hood latch and the brace appears to diagonal down in front of the short V8, so it's not a fair comparison. If none of that matters, "D" would probably be the stiffest from what I can tell looking at small pictures.