I completed a ride last weekend using the Third eye ( glasses mount ) mirror but with the mirror mounted to my helmet visor. I used a piece of electrical tape to keep it from falling off. Pretty much the perfect position the only problem was vibration. Not really the mirror's fault because the visor is somewhat flimsy. I might be able to eliminate most of the vibration using some soft foam and some tape to sure up the visor. Crossing my fingers hoping this will work.

The problem for me is that I wear prescription glasses. If I'm going to use a helmet mirror or a mirror mounted to my glasses the mirror has to be in the upper left corner but not out of range of my ( corrected ) vision as I'm looking through my glasses. There in lies the problem. People who wear glasses automatically have a limited FOV. Dialing in the right position is a real PITA.