1105.B.5:
"Arm Restraints. SFI or FIA-certified arm restraints are required
and must be utilized in all open-cockpit cars including formula
cars, and sedans with open targa tops, sunroofs, or T-tops."
1404:
"Sunroof. Production cars may be fitted with original equipment and/or after
market sunroofs. Sunroofs shall remain in a completely closed position
whenever the car is on the racing surface. For original equipment and after
market sunroofs made of glass or other breakable material, the Race
Steward may require that said roof(s) be taped in a manner designed to
prevent shattering in the event of an accident."
Take your glass roof to a fabricator and have them English Wheel you a steel replacement.
Do note that if you take out the reinforcement out of the sunroof itself on a sunroof car and your cat jumps on it from the rafters it will collapse inward. A quick bump on the underside will pop it back out (and scare the crap out of the cat).