Will this wing maintain stability at highway speed?

Yes. The AG profile is engineered to generate downforce across a range of speeds. Confirm that mounting hardware is torqued to factory specification and that the wing is aligned perpendicular to the vehicle centerline before first drive.

What mounting hole pattern does this use?

The wing is designed for direct mounting to factory attachment points on the deck lid. Before purchasing, verify that your current lid mounting locations are clear and not obstructed by aftermarket trim or previous modifications.

Will the wing interfere with a trunk lid or spoiler already on my vehicle?

The AG profile sits at a specific height relative to the deck lid. If you have an existing spoiler, confirm clearance and fitment with the two components before final installation. Interference depends entirely on your current setup.