Will this diffuser scrape on steep driveways or parking lot inclines?

The Silkstreak diffuser extends minimally from the factory bumper line. Check your vehicle's approach angle and compare it against your typical driving conditions — parking ramps, steep driveways, and gravel terrain are the real test. If you run lowered suspension, verify ground clearance before installation.

Does this add functional downforce or is it purely cosmetic?

This is a styling diffuser designed to enhance the visual character of the rear bumper. While the integrated vane profile mimics aerodynamic design language, real downforce benefits come from high-speed track use with proper geometry and angle of attack — confirm your specific driving needs before expecting performance gains.

What prep work does the FRP panel need before paint?

Sand the entire surface to create proper adhesion for primer and paint. After sanding, wipe clean with a tack cloth to remove all dust. Your paint supplier can recommend the specific primer and topcoat system for FRP — different shops use different products, so verify compatibility with your chosen finisher before starting.