My buddy at work saw my first RC car video and commented that I had configured the Xbox controls to be comparable to a traditional remote control car controller.
That is to say, the left stick makes the car move forward and back, while the right stick makes the car go left/right.
He suggested that I implement a more videogame'esque control scheme. A lot of driving games will have forward on the right trigger and backward on the left trigger. Also, steering is done on the left trigger.
I implemented this change and I believe that it works very well. Additionally, it frees up the right stick for future applications (e.g. pan and tilt camera).