Will this interfere with the trunk seal or body gaps?

The M1 Speed lip is designed to sit flush with the factory lower fascia. Verify clearance by test-fitting before final fastening, especially if your bumper has been modified or replaced.

Can I use adhesive, or do I need to drill through the bumper?

FRP lips work best with mechanical fasteners secured to existing factory mounting holes in the bumper. This approach avoids long-term adhesive creep and allows for clean removal. Adhesive alone is not recommended for sustained performance at highway speeds.

How stable is this at speed, and will it flex?

FRP construction resists flex under normal driving and wind load. Proper fastening to all available mounting points ensures stability. Avoid loose hardware and verify all fasteners are tight after the first few drives.