I'm setting off on a long trip tomorrow so I decided to deal with this today. I got a proper 8mm hex key and was able to confirm that the hole is still clockwise-threaded, at least down at the bottom. So I was able to attach the mirror extender properly.Unfortunately, no matter what I did I wasn't able to attach the mirror to the threaded hole in the mirror extender, which may (MAY) be threaded the opposite way. (By the time I thought to check, I'd worn away too much of the threading on both parts.)However, I was able to remove the mirror extender and reattach the mirror in its original position -- ONCE. After I removed it and tried to attach it again, it was too loose to hold. Apparently the overlap between (good threads on mirror stalk) and (good threads on mirror extender) was pretty small.So I just bought a tube of blue Loctite and will see if that provides enough grip to hold the mirror in place while I order a replacement mirror and a replacement for the thingamabob that the mirror screws into -- which my dealer will cheerfully install for me when I go in soon for my next regular service.In the meantime, today I built a RAM cellphone mount out of about 30 separate plastic and metal parts, and suspended it from the stalk of the *good* mirror on the other side.