I tried double sided tape and Velcro, best quality stuff I could find in both cases but in the end I used Alan head bolts. The other option didn't last.
Have a look at the 3M site, I used a mixture of the specialist double sided automotive tape & strangely enough the heavy duty command hanging strips at either end. Worked a treat for me
Mine are on with double sided pads/tape. Cleaned panel/bumper and plates with panel wipe first to remove polish buildup etc and have been ok for over 2 years.