Will this diffuser scrape on driveways or inclines?

The Twiller profile adds visual impact without extreme extension, so clearance risk is minimal under normal driving. Check the lowest point of your current rear bumper; if you frequently bottom out there, verify fitment with your vehicle's specific suspension height before installation.

Does this diffuser provide functional downforce or is it cosmetic?

This is a bolt-on styling piece. Real aerodynamic benefit requires a complete rear-end package (rear wing, underbody sealing, and chassis tuning). Use this diffuser to enhance the look of your rear end — performance gains come from the whole system, not the diffuser alone.

What surface prep should I do before painting?

Sand the surface with fine-grit sandpaper, clean with a tack cloth, and follow your chosen paint system's prep instructions. If you're unfamiliar with FRP finishing, consult a professional painter to ensure proper adhesion and durability.