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

The two-piece design is engineered to sit below the trunk line without contacting the seal. Verify clearance by test-fitting both pieces before final bonding. If your vehicle has aftermarket bumper modifications, confirm the diffuser profile aligns with your specific rear panel geometry.

What's the best way to install these — adhesive bonding or drilling?

Both methods work with FRP. Adhesive bonding is cleaner and reversible; drilling provides permanent mechanical security. Your choice depends on how long you plan to keep the car and your comfort level with fastener installation. Ensure the mounting surface is clean and dry regardless of method.

Will these stay stable at highway speeds?

FRP panels are rigid and won't flex under normal driving loads. Once properly secured and fully cured, they remain stable at speed. Apply your chosen finish per the manufacturer's specs to ensure the epoxy and paint bond fully before highway use.