Will this diffuser scrape on driveways or steep inclines?

The Patriot profile follows OEM rocker and bumper geometry, so it sits at factory height. Scrape risk depends on your suspension setup and approach angle — check ground clearance before final install if you've lowered the vehicle.

Does this add downforce, or is it purely cosmetic?

This is a cosmetic diffuser — it's molded to the OEM style and does not generate aerodynamic downforce. It complements the rear bumper appearance and reduces visual bulk compared to a bare bumper.

What prep and paint should I use on FRP?

Sand the surface with appropriate grit to scuff and clean, then apply a quality primer and your chosen topcoat. FRP accepts standard automotive paints and clear coat — follow your paint manufacturer's prep guidelines for best adhesion.