They come new with a padded tape approx 5mm in width, i would stick to something similar to absorb the shock from the road bumps, otherwise i would think it would be more likely to come undone.
Also make sure whatever you do you clean the contact area thoroughly on both the deflector and door with some Isopropyl Alcohol or something similar before you use any adhesive. Lots of people end up on here looking for a replacement for one side due to it falling off.
Hope that helps
Edit: Also the clips are a pain in the ass, i would'nt bother with them.