Will this lip interfere with the trunk seal?

No. The C-Speed profile is designed to sit below the trunk edge and clears the weatherstripping when installed at factory mounting points. Trunk operation remains unaffected.

Does this require drilling to install?

No drilling required. The panel uses existing factory mounting holes on the rear bumper panel. Standard hand tools and fasteners are all you need for installation.

Will stability be affected at highway speeds?

This is a cosmetic rear lip diffuser, not a functional aerodynamic wing. It does not generate downforce or impact stability. Performance changes are negligible at any speed.