Will this interfere with my trunk seal or undercarriage?

The V-Speed lip extends minimally below the stock bumper line. Verify clearance with your OEM bumper geometry and any existing undertrays before final installation. No modification to trunk weatherstripping is needed for standard fitment.

Should I use adhesive or drill through the bumper to mount this?

This lip is designed for bolt-on installation using the factory bumper attachment points. Drilling is not required. Confirm mounting hole alignment with your bumper fascia before assembly to ensure a secure fit without modification.

How stable is this at highway speeds?

FRP panels are rigid and remain stable under normal driving conditions. Ensure all fasteners are torqued evenly and rechecked after the first 100 miles of driving. Reference your vehicle's service manual for proper fastener specifications and torque values.