Trying my hand in some photoshop tricks. Hehe... This was fun. Don't know why there is some ghosting around the car though, I thought I was careful in selecting outside the car! Now I just need to get a new top. Hehe...
You probably had a "feather radius" on the outline of more than 10 pixels (or more depending on image size)... that would encroach into your outlined car then... try a 1 pixel and see what happens...
(I'm a senior graphic designer... and I'm actually taking a break from PS right now believe it or not! haha.)