Will this diffuser scrape on driveway inclines?

The corkscrew profile adds minimal vertical extension to the bumper line. Check your vehicle's current rear bumper clearance on steep driveways or parking lot aprons — this diffuser sits at the same depth as the factory bumper and won't increase scrape risk.

Does this diffuser provide any functional downforce?

This is styled for visual customization. The corkscrew design creates aesthetic flow at the rear, not aerodynamic performance. If you're seeking functional downforce, a larger multi-element diffuser would be the better choice.

What prep work does FRP need before paint?

Sand the surface to scuff the finish and promote adhesion, then clean off dust before applying your chosen primer and topcoat. Refer to your paint supplier's instructions for grit recommendations and primer type based on your finish system.