A bit over two years ago, I hoped my design for a bike helmet mirror mount would prove to be more durable than the fragile commercial mirrors I’d given up on:
Having just tightened the teeny screws that hold the joints in place for the first time since I glued it to the helmet, I’d say it’s working fine. The 2-56 elevation setscrew has worn a slight dent in the arc and the 3-48 azimuth screw worked slightly loose; the mirror didn’t fall apart, but the position wasn’t as stable as it should be.
If I ever re-do the design, I’ll try adding a recessed metal (brass?) strip along the top of that arc, as that’s the most finicky adjustment. Perhaps a shoe under the setscrew would be better?
Two years of road grit show up clearly against the yellow plastic, though:
For the record, those 2-56 setscrews require 35 mil hex keys; as Eks reminds me, any design requiring those screws is just crazy talk.
The Smell of Molten Projects in the Morning 
ABS does take well to a shot of Flat Black spray.
That’d be the stylin’ thing to do; maybe I should just give it a rattle coat right over the crud!
In a year or two we’ll need new helmets, at which point I’ll build new mounts in black PLA. I’d like to see how that works out, as bike helmets spend plenty of time warming up in the sun and PLA has a relatively low glass transition temperature.