To pass NC safety inspection, you are required to have an inside mounted rear view mirror and and outside mounted drivers side mirror. It does not mention the size of the mirror. See page 49.
http://www.ncdot.org/dmv/vehicle_ser...nforcement.pdf
So it might be nice to have a small mirror molded into the drivers side mirror mount. Either that or cut a section out of the OEM mirror housing, glue it back together and install a smaller miror surface. It might be fun to try if I was willing to spend $160 on a spare mirror to make the change reversable.