So I've come up with a great way to mount the thing to the car: Place the servo inside the body, mounted to a project box which is mounted to the body, this way there is 3-way support to the Pan & Tilt setup, and it's all using rubber bushings from other servos, so that there are no harsh vibrations.
Roughed out where to cut, then looking from underneath, I shined a bright light so I could see the trace marks, I outlined them with a blade then cut with a dremel tool:
Here's how she sits!
No problems rotating!
Because this is a smaller scale body, it was very hard to make this all work, it couldn't be too high, couldn't be too low, couldn't be too far left or right, still has to be able to tilt up and down and spin without being too high or low etc... there is about 1.5mm clearence to all sides, between the roll cage side and top, and the chair/center console side and bottom. Sometimes you just get lucky - and a company sells a camera called the GoPro haha!
ONE issue is that I cannot be looking far down, AND turn to the left of the car, the top left of the camera hits the roll cage - that's okay, it's only if I'm looking at the floor and looking left, which I'll just have to make sure I never do.