I really liked Surfalex2000 design, but I didn't wanted to use any screws. After a few iterations, I redesigned the model from the ground up, only using the original shape and proportion. The back door is not a must, only if you wanna lock your cars.
After printing the parts, you can use cuts of filaments (10mm long) to put into the wholes. Glue together the left, the right and the center part. I plan to make a version II later on, with more sturdy connections.