im really liking that but you used a stock height Super Beetle :) Those things are the bastard child of the VW world :) I took a really crappy picture of the front of my car. http://deluxeiron.com/racecar/front.jpg can you change the car by losing the bumper, stretching the hood down, skinny front wheels, raise the wheels into the fenders (lower the car). I really like it but I would get seriously heckled for wearing a Super Beetle on my back.
I had just grabbed the best front view of a beetle that I could find, having very little knowledge of the differences! :) I came at this second version by altering my original version but if you don't feel like it represents your car well enough, I can scrap it and do another version, traced straight off the pic you provided.
I always try to design for all possible uses but when I was putting this one together I had your t-shirts as my primary consideration. White ink on black shirts will flake/fade over time and after repeated washings. A design with a LOT of solid white area will outlast a fine-line design in terms of readability and lasting impact.