From the latest SCCA Fastrack (February) that the requirements for front and rear window straps and clips has been changed. Only GT, GTS & IPE classes would affected. We use the SCCA GT rules for our GT classes, require GTS to comply with GT safety requirements and IPE is allowed Lexan type windows. Here is the wording. Change is hi-lighted in :

9. Cars and Equipment
9.3.55. WINDSHIELDS/WINDSHIELD CLIPS/REAR WINDOW STRAPS
Polycarbonate windshields such as Lexan are allowed except in Improved Touring, Super Touring, American Sedan, B-Spec, Spec Miata, and Touring. Windshield safety clips and rear window safety straps shall be installed on all closed cars (except American Sedan, Spec Miata, Touring, Improved Touring, and Super Touring). Alternatively, no clips or straps are required if polycarbonate windshields and rear windows are securely bolted to the frame. Three (3) clips (3 inch x 1 inch x 1/8 inch) shall be bolted or riveted to the body at the top of the windshield. Two (2) clips (3 inch x 1 inch x 1/8 inch) shall be bolted or riveted to the cowl and extend over the bottom edge of the windshield. Clips shall be spaced a minimum of 12 inches apart.
It is recommended that three (3) – 1 inch wide strips of steel or aluminum be installed behind the windshield to support it from collapsing inwards if it becomes damaged. The rear window shall be secured with two (2) metal straps(1 inch wide x 1/8 inch thick) bolted or riveted to the body at the top and bottom of the rear window.

We suggest that competitors whose cars are required to meet the SCCA GCR preparation specifications monitor the SCCA website for monthly Fastrack update.