Great thoughts and suggestions.

The wire is from my little RV. It's onboard to handle up to a 50 amp service that is common to RV sites. However, I have an adapter which cuts it down from 50A to 30A.

Anyway, as I said, the "pins" come out of the plastic mount of the 50A plug. I can solder the wire to the pin, and then push it through and plug that in to an adapter and then into a 20A three-wire plug.

With a stand which could hold the wire and pin in the air I might be able to make it work. As it is, I don't have a stand, but could get one.

I think I'll try a $15 180 watt soldering gun from Harbor Freight along with a holder made for soldering and fly tying and try to pour enough calories into the connection fast enough to get a good joint. The "bigger hammer" idea.

Barring that, I really like the idea of soldering each wire into something which can be fitted into the connector. Genius.

Thanks again. Something will work.