Will this interfere with the trunk seal or rear bumper fitment?

The lip mounts to the existing rear bumper structure without modifying the trunk seal area. Verify clearance with your rear bumper cover before committing to drilling or adhesive installation — some bumper variations sit slightly different than others.

What's the best way to install this — adhesive or drill-through?

Both methods work. Adhesive is reversible and leaves no permanent holes; drill-through offers maximum security. FRP bonds well with high-strength automotive adhesive, but consult your mounting surface condition and local install preferences. Refer to your chosen fastening product's instructions for prep and cure times.

Will this spoiler stay stable at highway speeds?

Yes. The lip is designed as a fixed, non-articulating panel mounted directly to the rear bumper structure. Ensure your mounting method is secure — whether adhesive or fasteners — and the factory bumper attachment points are in good condition.