Will this interfere with my trunk lid when it opens?

No. The wing mounts at the trailing edge of the trunk lid using factory hole locations. Verify your trunk's full range of motion before final installation — most applications clear without interference, but checking your specific setup takes 30 seconds and prevents regret.

Do the factory mounting holes align perfectly, or will I need to drill new ones?

The wing uses factory trunk lid hole patterns, so drilling is not required if your OEM holes are intact. If your trunk has been modified or repaired, measure the hole spacing against a service manual or test-fit before committing to fasteners.

How stable is FRP at highway speeds?

FRP is rigid and holds up well to sustained speed. Once bolted down tight using proper fasteners, the wing stays put. The real variable is your installation — use fasteners appropriate to your mounting surface and torque them per your vehicle's service manual for fastener values.