I fixed my brackets to the stainless steel quarter light trim (silver soldered) and they seem ok to me, but they would be better with convex mirror glass in the assembly.
the one I had was attached to the long side of the quarter light not in the corner. It did not prevent the quarter light opening as it was attached to the frame not the glass
I found the ones fitted to the quater light uprights to be useless. Rear vision was very limited and it was necessary to move your head too far to see anything. I find without doubt that the MGB style mirror fitted to the doors and viewed through the quarter lights give excellent rear view,especially on motorways.
Here is a picture of it open. Is this the maximum that it can open (90degrees)? judging from the rubberseal design, it seems to me it is, but i am still not very sure cos its suppose to guide wind into the cabin and the mirror is actually blocking me from moving it to more than 90degrees.
Wing mirror fitment was a dealer option. As a consequence there were many different styles of mirror that were used and the locations all subtlely differed.
My understanding is that dealer fit mirrors were always on the wing rather than the door/quarterlight
You must have go-go-gadget eyes since all I can see of them is a wing mirror with a tiny bit of reflection vibrating about in the wind so much as to make the reflection useless ... maybe I need to get my eyes tested though
Flat glass wing mirrors are next to useless. I have them on my Traveller but can't get them off without serious damage to the wing.
I have convex mirrors on the Series MM and they are far better.