Will this interfere with the trunk seal or door jambs?

No. This is a front add-on lip that mounts to the lower bumper, not a hood or fender extension. It sits forward of all sealing surfaces. Verify clearance with your bumper's existing mounting points before installation.

Does the lip stay stable at highway speeds without additional bracing?

Yes. The one-piece design mounts directly to the factory bumper structure, which is engineered to handle aerodynamic loads. Ensure all fasteners are torqued to your vehicle's service manual specifications for optimal rigidity.

Can I drill into the carbon fiber to add custom mounting points?

You can, but it's not necessary—the lip uses OEM attachment locations. If you need to drill, use a carbide bit and work slowly to avoid delamination. Sand the drilled area and apply clear coat to protect the exposed carbon weave from UV damage.