That was so helpful.
My point is that they see no reason to discuss decisions that have been made with little input from engineers.

I agree, larger diameter is much better, but very difficult to live with in the car.
I limit my remarks to a single point of attachment, in which bending allows collapse of the adjacent tubes.

And my point is if you can build a better mouse trap go to the NHRA and get it accepted.

If you put a roll bar in a car you will actually have two.

I wrote something about a new product as sarcasm about 30 years ago, can't find it.
Ever hear of NIH? A force stronger than the hydrogen bomb, it protects important people from new ideas. Used by all car manufacturers and defense contractors.
NIH = not invented here.

A properly designed chassis is a series of triangles.

To your other comments...I'm certain engineers who are very familiar with the chassis in question, and the forces involved in accidents, are involved in the establishment of these specs and rules. Chassis builders, OE factory engineers, safety experts, sophisticated CAD and analysis, etc. Fuel cars, Pro Stock, NASCAR, Big bucks. That all filters down to the lower classes.

Unfortunately, it usually takes someone being killed to cause a serious look at the cars in question and get them updated.

He's smarter than all those people.

If they are welded to or through the floor!!

Both will work, I've used 2x2 as well as 2x3 .083 rectangular tubing for sub frame connectors in the past
It is up to you which size and how to have it installed

I used 2x2 .125” wall for mine.

You noticed that?

2 X 3 is much, much stiffer than 2 X 2, not just the obvious 50% height increase.

I agree 2x3 is stiffer, but the roll bar helps too.

Also drop the ends of the main hoop through the floor and weld them to the subframe connectors?

If you can’t bend/weld a bar in yourself, find a quality shop to install a moly 8.50 cert setup. Make sure you’re at the shop when they’re measuring/cutting and welding-in the main hoop and halo so they can build it around your actual sitting position while in the car. Not sure what belts, seats you’re using, but consider Kirkey’s or seats that would not allow your body and head to flop around a lot in the event of an accident on the street, i.e, keeping your body, head from contacting the main hoop and halo. If most of your time spent in the car is on the street, then I’d install door-side swing-out bars. Lastly, unless you’re wearing some sort of head protection, no way in hell would I ever run a car on the street with a funny car cage. I personally know two guys who died from head injuries when their heads smacked their funny car cage bars on the street. They were driving normal and were hit on the driver and passenger sides of their cars. They weren’t hot-rodding or acting like hooligans, just freak accidents. If anyone were to install or currently has a funny car cage they run on the street there is a company that makes a helmet shaped like a baseball cap that doesn’t look too goofy. It would at least allow you to live most likely.

Excellent, excellent advice!! As much as most of us do not want to hear that, it is very true. Thanks!!

I agree on using a racing seat and harness if you have a roll bar/cage. Anything lees than that (stock seats and lap belts bar or no bar) and you are at the mercy of a higher power in the case of an accident. The crash tests from the 60-60s era were brutal. One of the reasons I like beating on my cars at the track. Chances of a hard, head on front end collision are much lower with no telephone poles etc. At that point you end up abiding by the rules of where you race and add safety precautions for the street use.

A few things also come into play with design of the cage too. You don't want to be under the hoop. I have seen taller guys do this when laying the seat back or using a factory bench. It is acheived with a kicked out horizonal bar in the hoop instead of running it straight across so it does it's job. Bad place to be without a helmet, padding or not.

The other problem I see with the factory flip up seats of 67 and back is that they do not lock in position. Then you see the harness bolted to the floor behind the seat just right so in an accident the seat will fold you up as both it and you torso get intiment eith the dash. My 66 b bodies both have race seats because of this.

The rules say the hoop must be higher than you helmet so definitely check that as you put it together. For sure use swing out bars unless you are really throwing the world at it lol. I also like forward bars in our unibody mopars. Cab turned me on to the idea of running them outside of the fender apron. Way easier to work on the car with the bars out of the way.

Angling two bars that intersect the frame connectors from the main hoop( making it an 8 point) are extremely worthwhile regards chassis rigidity upgrade and making the car “ one piece”
In other words, these two angled bars would go through the rear seat footwell and weld to the frame connectors on each side.

In the drivers compartment, the only adjustment to be made to the bar locations would be fore and aft on the main hoop for leg room if using stock steering and pedals. Unless the driver is freakishly short or tall, that's pretty much a standard location. Back in the car a bit. The seat doesn't need to be against it. And the next guy to own it might want the seat to go back. The rest of it gets put in as close to the body/headliner/B pillar/ doors as possible to give as much room as possible. This usually takes some planning and effort to get it all welded up 100%. Helps to get the windshield out, Fast Super Stock and other stock body 25.x type deals or cars like a SN95 Mustang often have the roof removed to get it all done.

Frame ties are 2x3x.083, stood on end through the floor. Mopars get the back of it poked into the front of the stock frame rail, maybe half above and half below the floor. Section it up in so it fits up against the torsion bar X member, Outriggers from the frame rail to the rocker, also sectioned into the floor, provide solid mount points for the cage.

I would add the need for .125" wall FC is IMO reduced as one installs more cage components. I don't see many cases that .125" is required once one starts adding a roll bar+.. A pair of .125" 2x3 tubes are heavy for little gain.