Not the same car, but a couple weeks ago in Olympia I saw a red Miata with a dirt bike on the roof. It looked bigger than the car and luckily it wasn't a windy day.
Man, can you imagine going over a speed bump in that set-up? Sheesh. Likely to die from a crush injury.
And having ridden in a similar model, I can't imagine hills are easy to climb with all that weight considering the sewing machine that powers it! Whatever gets you there I guess...