Look guys the QRH is quite specific, it says in this event DO NOT ENGAGE EITHER AUTOPILOT. The reason is you no longer have a comparator crosscheck. YES you can engage an autopilot but dont, even if you decide to monitor it closely. This is one of the famous Boeing "we dont provide checklists for multiple failures" but infact that's what they are saying in this checklist, if you select an autopilot and something else comes unscrewed, you dont have any warning except from the SBY instruments which can easily go unnoticed now that you have removed the THIRD (and defining) instrument(s).