Will these diffusers interfere with a factory trunk seal or weatherstripping?

No. Merella rear diffusers mount to the lower bumper fascia, not the trunk lid or hatch seal. Verify clearance against your vehicle's rear bumper corners before assembly, as aftermarket bumpers or other body mods may affect fitment.

Do I need to drill mounting holes, or is this adhesive-only?

The two-piece design uses a combination of mounting methods depending on your bumper type. Before ordering, inspect your rear bumper for existing holes or tabs that align with standard diffuser anchor points. If your bumper lacks factory attachment points, fastening will require drilling or adhesive bonding — confirm your preferred method before installation.

Will FRP diffusers stay stable at highway speeds without additional bracing?

FRP is rigid enough for aerodynamic styling at all speeds when properly mounted. The two-piece construction allows you to secure each section independently, which improves stability. Ensure all fastening points are fully tightened and regularly inspect for any vibration or movement after 500 miles of driving.