John:
I use an IO Port roll bar mount with an old Canon Elura video camera. The Elura has a provision for an external mike (which I highly recommend) and I use a simple lapel mike clipped to the lower part of the passengers seat belt where it's out of the way. As mentioned the onboard mike picks up a tremendous amount of wind noise that's very annoying.
The IO Port mount is extremely flexible as far as positioning the camera goes and, with a light camera, very rigid.
Here is a sample of one of the tapes from this past summer with the Colorado club.
DonC