If I remember correctly, for cars 1500 lbs and under, both front and rear hoops were 1.375"dia. .095 wall. DOM
Braces for hoops 1.000"dia. .080"wall DOM.
Front hoop braces to front bulkhead.
Rear hoop braces, for or aft , min 30° inclusive angle and down to chassis rails. .080" gussets
I'd looked this up in the GCRs but cannot find it now that I need confirmation..
Have the rules changed recently or have I not looked in the right section?
All I found was page 148 "Roll Cages"
Chris