Following the usool of Imam Ahmad technically makes them hanbalis.... Because of the format of the madhab and it's usool. Most if not ALL of the Hanabilah have had iktiyaraat and didn't stick to the "mufta bihi" because of the fact that the Hanabilah scholars were more willing to do ijtihaad and follow what they thought was correct. There are Raajih opinions, however sometimes even the Shaykayn of the Madhab go against the Raajih for what the deem more correct. So in actuality following what he the Mujtahid deems more correct even if going against the "Madhab opinion" is closer to the Madhab, because of the Usool of the Madhab.