Nevertheless, original advice for the d800 handheld was 3x, and I found in practice that this was the only way to be sure. It doesn't matter, in a way, that I can also very often nail it at 1x because I know that I might not. So my way, when there is time, is to shoot my a7r at 3x at whatever ISO that requires, then, if that ISO is 'too high for comfort' bang off a few frames at lower ISO and lower multiple of shutter speed.. I will generally get at least one frame that works at the slower shutter speed, but have my insurance policy in place. However this clearly does not suit all subjects and situations...
If I were writing a petition to Sony it would be to allow AUTO ISO parameters to include a variable minimum shutter speed linked to focal length...