As we can see, everything can be done. It is totally possible to have a good bolt in bar/cage if done correctly. Were I see a problem in most cases is that people who want bolt ins want to do the least poissible modification to the car and so some of those bars are only bolted to existing OEM holes and bolts, sometimes on top of the carpet. This is a poor design that can fail. A proper bolt in must be as strong as a welded design, I rarely do bolt ins but if I do I refer to my bible:
http://www.fia.com/sites/default/fil...%282013%29.pdf
When I built Tonybest bar I did not want any compromise, so it is built so that one day a front section can be added and it will pass tech anywhere (used the FIA standards for the back part), I also considered the space, that why the bar is a bit behind the b pillard. So no funky bended tubes.
Fullerra bar is nice for a compromise setup and will most likely do what's it's supposed to, but I personally would not build a bar that is not made and based on racing rule books, welded or bolt in. I recognize that something is better than nothing.
I know I'm hardcore but I don't f?*k around when it comes to safety. (that is a totally personal comment and I don't take anything away from any cage builder/fabricators)