Will this interfere with my trunk seal or bumper engagement?

No. The two-piece design mounts to factory attachment points and sits flush within the existing bumper profile. Before installation, verify that your OEM bumper mounting brackets are clean and secure — any worn hardware should be replaced to ensure the lip sits evenly.

Should I use adhesive or drill holes for extra security?

Factory mounting points are sufficient for street use. Adhesive is optional if you prefer additional reinforcement, but it is not required. If you choose adhesive, apply it only to the contact surface after sanding and prepping both the lip and bumper. Do not drill through FRP unless absolutely necessary, as it can create stress points.

Will this lip stay stable at highway speeds?

Yes, when properly seated at factory mounting points. Before hitting the road, double-check that all fasteners are tight and the left and right pieces are aligned evenly. A slight gap between the two panels is normal; they do not need to meet perfectly flush. Verify alignment one more time after your first 50 miles of driving.