Will this lip interfere with the front bumper when the hood is open?

No — the lip mounts below the bumper fascia and does not extend into the hood opening. Verify alignment with your bumper's mounting structure before drilling or fastening. If you're running an aftermarket bumper cover, test the gap between the lip edge and fascia to confirm clearance.

What's the best way to secure this to the front bumper?

The lip is designed for fastener attachment at OEM mounting points. Use the factory bolt holes in your bumper fascia as your reference. You may need to drill pilot holes into the lip itself depending on your bumper design — align the lip first, mark hole locations, then secure with appropriate automotive-grade fasteners. Consult your vehicle's service manual for fastener torque specifications.

How stable is this at highway speed?

FRP rigidity resists flexing and vibration under load. However, ensure all fasteners are tightened evenly and regularly re-check them after 500 miles of driving — any looseness will create movement. Proper mounting technique is critical to handling stability at speed.