Will this interfere with the trunk seal or rear bumper panel?

The front lip mounts to the lower bumper fascia and does not contact the trunk or rear assembly. Verify clearance with your specific bumper configuration before final installation to account for any prior modifications or non-OEM components.

Do I need to drill into the bumper, or can I use adhesive?

Both methods work depending on your preference and existing mounting points. Inspect your bumper's underside for factory holes or attachment tabs that may align with the lip. Adhesive alone is viable on smooth surfaces; drilling offers redundancy if you want permanent security. Prep and degrease any mounting surface thoroughly before committing to your method.

How stable is this at highway speed?

FRP lips designed for under-bumper mounting sit close to the body and experience minimal high-speed buffeting when properly secured. Ensure all fasteners are tight and any adhesive has fully cured before highway driving. Inspect regularly for movement or stress cracks, especially after impacts or rough terrain.