Will this diffuser scrape on steep inclines or driveway approaches?

The Juku profile extends the lower rear bumper line moderately. Check your current ride height and driveway angle before installation. If you frequently encounter steep ramps or unpaved surfaces, test-fit and verify ground clearance at your vehicle's lowest point. FRP is durable, but prevention beats repair.

Does this add functional downforce or is it cosmetic?

This is a styling piece. It enhances rear-end visual aggression but does not generate aerodynamic downforce. For genuine aero benefit, you'd need a full diffuser system integrated with the underbody. This diffuser is built to look sharp and complement your bumper line.

What surface prep should I do before painting?

Sand the raw FRP panel with standard automotive-grade sandpaper and wipe clean of dust before applying your chosen base coat or protective finish. Follow your paint manufacturer's prep instructions for best adhesion and durability.