I always applaud any effort to DIY. Just keep in mind that with the mirror so far away from your head your ( rear ) FOV is going to be very small. When dealing with mirrors like this there will always have to be a compromise between the following; FOV, position, useability and geek factor. Almost nothing will be perfect. I can deal with limited FOV ( to the rear ) as long as the mirror doesn't block my forward FOV too much. "Geek Factor" is the last thing I worry about but is still a consideration.

On my last ride ( rural country roads ) the mirror gave me advance warning of approaching traffic before I could hear them. Mirrors work as long as the road is not too curvy, the elevation is fairly stable and you have good line-of-sight. If you're flying down a section of road that is curvy/rolling hills and you're riding at speed ( > 20mph ), it is still going to be very hard to keep track of what is approaching from the rear. The more attention you have to give to what's in front of you the harder it is to monitor the rear.

I don't know how people can discern details of approaching rear traffic with these mirrors. With my head constantly moving ( the faster I go ) getting a target lock on rearward approaching traffic is not always easy. Usually if I can make out a pair of headlights or the front of a car I'm happy. I don't worry about the details. Too much potential danger in front of me ( road debris, pot holes, cars, people...etc ) to be spending too much time gazing into a rear-view mirror.