I have a 4 point roll cage, with bars going into the trunk. I am thinking about going to 6, with 2 along the doors. Am I allowed to use rings to attach the main segments to the existing cage or must they be welded at that juncture? This would be for something going low 11s, but I am thinking ahead to a day when I may make the changes for high 10s.

Also, I've seen many cages with two extra supports under the horizontal bar behind the seats. I can see the pros in that, but what are the rules? The cage is painted so I'm trying to see what I can do without having to weld and re-paint. Thanks.

NHRA 5 point is all you need down to ten flat,just need the door side bar, if you have unaltered floor and firewall...Swingout door bars are good to lower than that I believe.. That being said when my car hit 11:5's I did an 8 point with the diagonal supports you mentioned tied into the subframe connectors.I wanted to stiffen it up a bit... the link gives tubing size and diagrams. You have to weld the door bar/swingout mount to the main hoop and land the floor attachment on a 6x6x1/8" plate, the plate can be bolted to the floor but the bar/swingout mount has to be welded to it...99% sure.. Bar rule

What is meant by modified floor pan or firewall? I have subframe connectors welded into my floor and patched rusty places in the firewall. Does this fall into medifications or do they meaning moving the firewall and such.

Subframe connectors & firewall patches won't be a problem with Tech.
If you go with a 6-point, tie the hinge pillars into it and run a bar between the hinge pillars and the shock towers.

What do you mean by hinge pillar? I am very uneducated on cages.

The hinge pillar is what the door hinges attach to; big boxed vertical panel. Major part of unibody stiffness.

Ahh that is what I thought. What is the bar called that runs along the roof then meets with the door bar.

halo