Dick's correct (I'm looking at the '09 GCR now).

- If your car was registered prior to 1/1/08 your car is subject to the rollcage rules in "Appendix G. 2007 Roll Cage Rules" (p GCR 147). There you'll find references to different weight classes and the note that IT cars subtract 180 pounds to determine tubing size.

- If your car was registered 1/1/08 or later, your car is subject to GCR 9.4 "ROLL CAGES FOR GT AND PRODUCTION BASED CARS" (p GCR 88). Therein is a list of weights and rollcage tubing sizes, with no 180# exemption for IT cars; ergo, rollcage tubing size is dependent on classified weight (i.e., with driver, horn, and hood latches - if installed).

Note that there are some distinct and tricky differences in wording with the new rules, especially in regard to optional tubing; it's best you read those new rules carefully if you are building/built a new car after 1/1/08...

GA