Not all tech inspectors are the same but here's my guess:
I'm betting they'll okay it down to 10.0. That's what I was approved for locally by welding a full width roll bar in and adding a door bar on the driver's side (make sure to bring pics of the bare frame, some of the tech inspectors think the cars are using fiberglass as a supporting part of the frame). I believe the design/quality of the frame is what impressed them and allowed me to go faster than the typical 11.0 limit for convertables. The okay I got was from an inspector who I e-mailed pics to. He replied with the okay down to 10.0. I printed that out and brought it to the track along with the pics.
To go below 10.0, you'll have to go overhead with the cage, get it certified, and that's where they really start looking closely at the thickness, diameter and type of metal used for the entire cage.
If you want to go under 10.0, look closely at the rules, compare it to the specs on the car, maybe even send the frame pics to an NHRA inspector. That way you'll know if you just have to add to what's there, or cut some out and start over.
Last edited by tommyg; 10-05-2010 at 07:43 AM..