Keeping clamp-on tow mirrors on

Anyone use these (or similar) CIPA extension towing mirrors that I got in yesterday? If I mount them from the top where the inner mirror bezel sticks out further than the housing, the clamps don't get as secure a bite.



Mounting them from the bottom gives a better grip for the clamps since the bezel and housing merge there.



Question is though, how can I make sure if these vibrate loose on the road do I keep them? I'd hate to lose one or both that way and I sure hate them damaging some vehicle following me. I'm thinking I'm going to have to zip tie them somehow. Anyone have a suggestion?

 

I mount our Milencos on the bottom - but I jam the rod against the edge of the door. In the last 7 years these have never moved, nor have I ever been concerned about them falling off.. You could always loop something like a shoelace around the mirror and through the clamps, but then I would be more worried about that banging against my truck if it came off.