My supercharger uses a serpentine style drive belt. Do I need a “pop” off plate if it backfires?

No. The serpentine style drives do not require a “pop” off plate. If the engine backfires it will slip the belt on the pulleys. If the blower is running a Gilmer (tooth) style drive setup then it does require a “pop” off plate. If a backfire occurs on a Gilmer drive setup the belt will NOT slip and it may lift the blower off of the intake manifold.