Will this interfere with the factory bumper seal or trunk area?

No. The lip is designed to mount at the lower fascia attachment points without contacting the bumper seal or trunk line. Verify clearance at the mounting points before final fitment to ensure the panel sits flush against your bumper.

Can I use adhesive instead of drilling new holes?

Yes. The lip can be adhesive-bonded to the factory bumper if you prefer not to drill. Use an automotive-grade epoxy or polyurethane adhesive on both the mounting flange and bumper surface, and allow full cure time before driving.

How stable is this at highway speeds?

FRP lips are lightweight and flush-mounted, so wind loading is minimal. The panel's rigidity depends on your mounting method — drill-through fasteners provide the most stability, while adhesive bonding is secure if the surface is properly prepped and cured.