In that case, you're better off with a stranger. I have no doubts that a scene with a friend will lead to expectations, if not his (unlikely imo,) then yours or hers... and unless such curiosity proceed exactly hand in hand, one or the other of you will be hurt.

Remember, today's boundaries have NOTHING in common with tomorrows fantasies and new boundaries. And then, if you do decide jointly to explore further... will you want to with your friend? Likely not imo.