I agree, urethane for the bumper.
cf is stiff, light weight, and well suited for many applications. But it’s probably not what you want on the street, due to initial cost, and high cost of a specialty shop doing repairs, if an unfortunate event were to occur. It also must be kept from UV, with some sort of protectant, which normally negates the "cool factor" of the exposed weave of the fiber.
One other thing...cf is not corrosive by nature, but when in contact with AL and moisture...you will have an electrolysis effect with the metal. The contact area must be protected using fiberglass.
The choice is really up to you.
