This mounting was not dreamt up by myself.. These upgrades came from Hi-Tech, they are the MFG. Hillbank/Superformance told me where to look for installation.
If you were to look at the upper cross member you would notice it attached to the shock mount and part of the cars frame.. Now I can't imagine Hi-Tech Superformance putting these pre/cut drilled belt mountings in their roller unless they were safe??
I do know that I would want the passenger to have shoulder harness in case of a front end collision, unless you want their face in the dash/windshield. As far as a roll over I also think the harness would help them stay in the seat.. If you were going fast enough for a roll over a helmet might help also
I have no pictures, Look above the shock mounts with tires off, you can see through to the other side of the car. In the SPF there are (2) cross members a lower and upper. These are both part of the cars frame. The top one has a 2"-3" slit in the fiberglass about centered with the seat backs. And a 1/2" hole is drill through the frame. You will need a "Y" harness I chose Simpson cam lock works great. (some tracks will not allow this). But it was more of a safety issue with me...
Hopes this helps..