Bolt in Harness Bar don't do it!!!

I specialize in Motor Vehicle Accident Investigation and Reconstruction and I have been watching this post silently from the beginning trying to determine an educated decision on this. After looking at the design, it is not really going to matter which placement position you use, in a serious accident it will most likely have the same reaction caused from the given pivot points.
They way I see it is:
In a newer car (import or domestic), safety wise, it is definitely not better than a factory set up.
For an old Mopar with lap belts only, it is not a terrible idea. It is an upgrade over the stock lap belts as it gives you a little more support/safety as what you are looking for. Would I do it, probably not. I would save my money and put in a hoop with a crossbar that has the needed attachment points for a more permanent set up, but that is not an option for everybody.
It appears that you are defending it, looking to justify to yourself spending $169 on it. For more safety than your stock set up at safe driving speeds, yes, it is probably worth it. In a 12 second car, that is going to be raced and driven hard on the street, I would not do it.
Over all, it seems to fit the purpose you intendit to.