Since the interior changed between 2005 and 2006, I'm guessing that the spot on the right side of the steering column mentioned by several 2003 owners doesn't exist on the 2006-2007 models.
FWIW, I mounted my Prodigy P3 on the upper left knee panel, right below the headlight switch. I popped the little dummy cover off of the dash where the power pedal switch was supposed to be mounted, and ran the controller cable through that hole and right into the back of the P3. I have never hit it with my knee, but it does stick out enough where I could see someone else kneeing it while climbing out.
With that said, I am on the record saying that I *hate* the P3 because it only has a single-axis accelerometer inside. This means that it doesn't work great unless it is mounted horizontally, and mounting it where I did is pretty close to its 70-degree maximum permitted mounting angle. On my list of things to buy is a Hayes G2 controller, which is tri-axis and looks like it will mount flatter than the P3 in the place where I have it mounted.....