Will this interfere with the trunk seal or bumper fitment?

The CS style lip is designed as an air dam extension below the bumper line, so it sits independent of the trunk seal. Verify clearance to your front fender liner and bumper reinforcement before final tightening.

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

This lip is engineered for bolt-on installation using the factory M Package bumper mounting bosses — no drilling required. Use fasteners appropriate for plastic-to-bumper connection and torque per your vehicle service manual.

Will this lip stay stable at highway speeds?

FRP construction and factory-point mounting provide solid stability at speed. Ensure all fasteners are tight and the bumper itself is in good condition; a loose bumper will affect the lip's rigidity regardless of material.