Playing with two-lug 220v current today. (Wiring in an RV receptacle.)
This kind of thing makes me nervous as hell. It doesn't help that the last time I did this a pair of actual certified electricians (my daughter and a friend) helped me – and they were nervous as hell.
And this time I'm doing it on my own…
I guess the moral is: Don't trust an electrician who ISN'T nervous as hell when playing with 220 volts at 50 amps.