[Showdown]

3 point harness wasn't hard at all. My car has lap belt pickup points so all it needed was the top point. As I mentioned, I took a 1/4" thick steel plate, roughly 4"x6" and welded it to the underside of the top of the area under the window from inside the engine bay- I guess we can call it the rear shelf. I drilled a hole through that steel plate and through the sheetmetal shelf as well as though the vinyl and padding. Yes, that's permanent damage to the vinyl but I don't care and if I ever remove the harnesses, I can get a small plug and cover it with matching vinyl and nobody will care.

The bolt was 1/2" if I recall correctly and with a fender washer and lock washer it was snugged down tight.

I suppose if I were to do it again, I might consider welding a full width bar across the entire shelf and gusset it against the inner side of the engine bay... that would be super overkill but not much more effort...

Would it pass NHTSA... probably not for a million reasons but it holds the kids snug so that they dont' flop around and in the case of a small accident I'm confident that they'll be held secure. In the case of a major accident, we're all likely riding the Nurburgring in the sky...