Will this wing stay stable at highway speeds?

Yes. The single-piece FRP construction is rigid and designed to handle sustained high-speed driving. Ensure all mounting fasteners are torqued securely before driving — refer to your vehicle's service manual for proper fastener specifications.

Does the wing sit flush with the trunk lid, or does it extend beyond it?

The A Spec design mounts using your factory hole pattern, which means clearance and extension are determined by your vehicle's original trunk architecture. Check your trunk lid height before installation to confirm adequate clearance with any modifications you may have made.

What prep is needed before painting?

Sand the surface with appropriate sandpaper and apply your chosen primer and paint system. Standard automotive prep techniques apply — clean, sand, and seal before color coat.