So I messed aroudn today from boredom and came up with this. let me know in the comments what do you think of it :)
Nice. My only crit is that the backplate looks quite HDR'y (no over OR under exposed parts) whereas the car looks like normal exposure (with shadow areas around the back). Im not sure how you get round that other than rendering out several exposures of the car and combining them into an HDR image before putting it over the backplate.
But I'm just being overly picky
Ed
The blowout on the roof and the back window is a bit much to me.