Will this diffuser scrape on steep inclines or driveways?

The diffuser is designed for wide body fitment, so final ride height depends on your suspension setup and stance. Measure your ground clearance at the rear quarter panel before final installation. If you run lower suspension, test drive on your usual routes to confirm clearance matches your expectations.

Does this provide functional downforce or is it cosmetic?

This is a styling piece that completes the GT300 wide body look. It's not engineered as a functional aerodynamic element. Its value is in completing the visual design of the wide body conversion.

What prep work does the FRP need before painting?

Sand the surface thoroughly and wipe clean before applying your chosen base coat and clear. Proper surface prep is essential for paint adhesion—do not skip this step. Follow your paint supplier's recommendations for primer type and application method.