Here is the constraints layer:
For perspective, imagine you are standing outside the car, off of the right (passenger) rear tire, looking toward the steering wheel.
The fire wall is obvious, the roughly rectangular pattern top center is the roof line from an interior point of view, the angled segments top and right are the A pillars along either side of the windshield, and the green balls are the left and right ends of the dash board where the cage has to clear them.
Next I've turned off the constraints and turned on the tubing layers:
Here the main hoop, the horizontal brace that goes across the cockpit at the shoulder belt attach line, and the side hoops that surround the door openings, are the only parts that have been mocked up so far. The rest only exist in the drawing, and are subject to change. I'm sure I will have to adjust the X brace at the fire wall to allow for access to the engine hatch. The struts back to the rear wheel house attach points are just a first guess also.