Nice set-up.

One suggestion to make it even more stable for track or auto-x use: Make the bar long enough to straddle BOTH headrest columns (it is easiest when the seats are back equally from the dash).

I also suggest some sort of back-up strap to catch the camera in case it does take a leap - maybe velcro/rubber bands around the entire unit -(cameras aren't inexpensive these days).

I made the same mount for my camera for <$40 as well.

I've been looking at doing the same thing for auto-x use. I'll ditto the backup strap comment. make sure that it's short enough that the camera can't contact the driver. For auto-x or track use, I'd probably rather not have the bar mounted to the driver seat, and I wouldn't want the camera so close to my helmeted head. If I was going to mount on a front seat, I'd use the passenger seat even if the video angle would be further from the driver POV. Ive the bar straddles both front seats, I'd move the camera closer to the passenger side. My plan was to mount it to the rear seat headrest posts.

How did you guys fasten the bar to the posts? I like the speedmount. It looks sturdy and durable and the holes are pre drilled (although it would probably preclude use in a differnt make/model car). Also, if I built one myself, I'd probably go overboard on the ball head...but that wouldn't be such a bad thing

In addition to what Emission said, I would like the camera further right and higher. I think it is too low.