Mix it up! There is no need to keep it in one spot for the whole time. We (the guys who are going to make the film at Rally9) have stuck GoPros anywhere they can be stuck to a car, and some of the best shots were happy accidents, or places we didn't think would work out well. That being said, if you are going to move the camera around, make sure that you shoot up high on the car first and not behind the wheel on the side (which I agree is a fantastic angle) unless you have a lens replacement kit handy. The road debris coming off the tire will sand blast the lens on the case and the rest of your shots that day will look like s***. Best thing to do is to spend some time in the garage, placing the camera on the car and using the GoPro app to align your shots, see which ones you like and remember them for track day. Make sure the mounting spot is clean (we even use isopropyl 70% wipes sometimes to clean the mounting spot), shoot at a high frame rate to avoid the 'jelly effect' and don't necessarily keep the camera in widest angle mode the whole time, the medium and narrow angles can be effective as well (and they are less fisheye and more 'cinematic').
Hope this helps out, I/we are truly looking forward to meeting all of you in Vegas and making an awesome little film.
If you shoot a bunch of angles and want it edited, I can do that. If you have any more questions and feel like emailing me, I'm always happy to chat.
Justin@LetsMakeMedia.com