Wow. Good info Vicegrip. I definitely wouldn't want to make things worse with a rollbar. I'm wanting one for protection.
I wonder why this bar was not made to the "track" specs you mentioned. Seems like it wouldn't be that much harder to do.
True you would think it is not much harder but some folks build for looks or without careful study. It might not be a bad bar but there are things that could have been a bit better for the same materal and effort.
Look at some pro built race cars and you will often see the same design aspects regardless of car. BMW, Porsche, GM or Dodge, physics and energy absorption is the same. The only laws you can't break are Newton's. might be worth the time to check in at the SCCA website. SCCA has some of the more extensive and detailed rules on cages. You can often learn "why" from the rules.
I fully understand the desire to add rollover protection to a convertible. Yours is a good idea and I bet it can be done and without a lot of machination, money or complex install. Geometric design strength, solid mounting points that are as strong as the bar and up to the task and functional separation from the humans it is there to protect.
It might be worth the time to find a fabricator that builds SCCA legal or better race cars. I bet you can find a good off the shelf bar too.
If not you can also go the tuner route.
There was/is a company called Monkey Bars or something like it that sold fake roll bars and roll cages for street tuner type cars. They were made from PVC tubing and you were to cut and fit the PVC tubing and then glue/screw attachment feet to the dash and floor boards as needed then covered it all in foam to make it look real.
