Go back in aviation history to when real men were flying wartime bombers with the most rudimentary autopilots and getting shot at and no weather radar either.
Although it should be noted that loss rates were extremely high - and loss rates due to accidents were comparable to losses caused by enemy action. Just a thought.
But "overloading" a PNF? If that is so then the PNF needs re-training to enable him to cope with his normal duties.
Well, I'd say any idiot can overload their PNF if they put their mind to it, whether hand flying or not. Who needs retraining? The overload-er, or the overload-ee?
pb