In case anyone is interested, I just put a set of 1200GS mirrors I had kicking around on my 2012 F650GS. No problems doing so, the thread size into the base is the same so no need to loosen the lever bases. Just lift the rubber boot, unscrew the 650 mirror, screw in the 1200 mirror, tighten the base and the locknut, and push the boot back down.
They are slightly longer without being overly long and the rear vision now just clears my arm. :brad