Will this interfere with the trunk seal or bumper when the trunk closes?

The W-1 lip extends downward from the bumper without adding rearward projection, so clearance with the trunk seal is not an issue. If you have aftermarket bumper reinforcement or diffuser elements installed, verify the lip sits flush against factory attachment points before final fitment.

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

This lip uses factory mounting holes in the bumper. Bolt through the existing holes — no adhesive or additional drilling required. Use the fastener pattern that matches your vehicle's OEM bumper attachment design.

How stable is this at highway speed?

FRP is rigid once bolted to the bumper frame. The lip sits close to the bumper line and does not create front-end lift or vibration. Ensure all bolts are tight after installation and periodically inspect them to prevent loosening from road vibration.