Just make sure your thumb stays below the string. I can tell you from experience it is painful and expensive. Granted I have unusually large hands.
You would think all the lawyer stuff in the manual in big bold letters would have prevented it. You only make the mistake once and you will ask and answer this question every time. "Where is my thumb?" "My thumb is down".
Im not trying to disparage the use, just want other to learn from my mistake. It isn't easy to post in a public forum you were dumb enough to do it!