I'll start by saying that when I first started I had only an idea of how intense the development process would be. This is one of those situations my vision of big giant brake rotors and calipers yielded to what that development process was saying was the best way.
The prototype started out with basic 4-piston calipers and 13" rotors all around which worked right off the bat, switching to 15" rotors numbed the cars performance with little gained in actual braking, I swapped calipers, pads and countless master cylinder combinations. It was my first personal test. I stepped back.
The irony of big rotors is it takes a lot more to slow them down, the 15" rotors needed a lot more heat just to slow the rotors down then they have to slow the car, worse you need more power to accelerate as you spin up that extra mass x 4. They made the whole car heavier. I'm building a light nimble car with fast reflexes to match, it was alway in me to put performance and total function above all. I could have dumped more money and energy into the big brakes to make them more to what I needed, but it would only be eyewash. I had something that worked instead of advancing that I went for a version of what was on every other super car thinking thats the way. I ended up with is a 13.8 inch rotors mated to 4-piston calipers all the way around this happens to work extremely well and while there's probably a better system out there I'm not sure it involves bigger rotors or calipers, for the moment this is one of the best setups for this car.
Right about now you're thinking carbon-ceramic, I wouldn't order my own car with em! I was benchmarking, a Porsche when piece broke off one of the rotors killing my track day plus generating a nice $1,500 bill (supposedly a bargain) not to mention tow charges. I don't need failed rotor I didn't make associated with my car or company.
Steel rotors are heavy but they can be treated so issues of failure are greatly diminished, I frankly get better feedback and one more thing I can get more stopping power out of a lighter set of smaller diameter brakes than the big 15" rotors.