we pre-twist solid but not solid to stranded.We make the stranded 1/8" longer at the top so the when the wire nut is screwed on it folds the stranded over the end of the solid and locks it down,so to speak.Then tug test the connection.
Heard this from a rep at the yearly trade show.
A few months ago a bad #18 solid to stranded joint almost brought our entire powerhouse.
cheers
