Will this interfere with my trunk seal or rear bumper at speed?

No—this is a front lip, so it sits at the lower front bumper. Just verify ground clearance on your specific setup; ramps and steep driveways are the typical concern, not aerodynamic interference.

Can I install this with adhesive only, or do I need to drill?

This lip is designed to use factory mounting points on your bumper, so drilling is not required. You'll be bolting to existing attachment locations—verify those holes line up with your bumper before starting.

How do I prepare the FRP before painting?

Sand the entire surface to scuff the gelcoat and create adhesion for primer. Once smooth, wipe down with a tack cloth to remove dust, then apply your chosen primer and topcoat system.