Originally Posted by Beemerboff
I don't think the mod is unreversable - the existing hole is nominally 8 mm with a decent bit oversize for powdercoat , etc, probably 8.2/8.3 mm.
The daylight opening on a 10 x 1.25 tapped hole is 8.75 mm so the difference in opening size is less than 20 thou, which I don't think would stop you refitting it OEM mirrors when the time came to sell.
If you Helicoil or Timensert, you tap a much bigger hole. Then you are reversing the threads on one side so that one is shot...and the 8mm thread will stuff in a 10mm hole but won't fit right. Using brackets is reversible. Take the brackets off.