CAR roofs, how to make them

[torikoos]

Is there a reason that you don't want to use an existing roof from an existing model?

Apart from the challenge, and learning something new, I also want to work towards my NMRA Master builder motive power certificate. That's the main reason why I want to make as many parts from 'scratch' as possible, to earn extra points. I prefer styrene as my main building material, but of course will use brass, balsa wood, or anything else suitable where needed to make a successful model.