I have Mountain Myrricles on both bikes, and love them. They give an excellent view rearward on the left bar.

I set mine up to make my bars as narrow as possible, and still be able to see well.

Starting at the bar, I point the first bar straight forward, and the next one UP. Then adjust the mirror itself, and make small adjustments of the stalks to see rearward.

Then, I tighten everything down, good and snug.

Hope that helps.